Occurrence of heparin in the invertebrate styela plicata (Tunicata) is restricted to cell layers facing the outside environment. An ancient role in defense?

Butyrate Increases Heparin Synthesis and Storage in Human Mast Cells

Sulphated glycosaminoglycans (GAGs) such as heparin are a major component of mast cell granules and form the matrix within which biogenic mediators are stored. Since GAGs released from mast cells also play an important role in helminth expulsion, understanding GAG storage can offer new insights into mast cell function. Sodium butyrate (NaBu), a short-chain fatty acid, causes ultrastructural changes within the granules of human mast cells (HMC-1) and increases their histamine content. Therefore, we hypothesized that NaBu treatment would also modify the storage of polysaccharides such as GAGs. NaBu (1 mM) significantly increased GAG content and granularity in a time- and concentration-dependent manner without affecting cell viability and metabolic activity. NaBu increased the expression of enzymes associated with heparin biosynthesis (GLCE, NDST1, NDST2, HS6ST1, and GALT1) in a time-dependent manner. A cholesteryl butyrate emulsion (CholButE) increased heparin content after 24 and 48 h and modestly altered the expression of genes involved in heparin biosynthesis. Similar to NaBu, CholButE reduced cell proliferation without significantly altering viability or metabolic activity. These data show that butyrate increases the synthesis and storage of heparin in human mast cells, perhaps by altering their metabolic pathways.

On Connective Tissue Mast Cells as Protectors of Life, Reproduction, and Progeny

The connective tissue mast cell (MC), a sentinel tissue-residing secretory immune cell, has been preserved in all vertebrate classes since approximately 500 million years. No physiological role of the MC has yet been established. Considering the power of natural selection of cells during evolution, it is likely that the MCs exert essential yet unidentified life-promoting actions. All vertebrates feature a circulatory system, and the MCs interact readily with the vasculature. It is notable that embryonic MC progenitors are generated from endothelial cells. The MC hosts many surface receptors, enabling its activation via a vast variety of potentially harmful exogenous and endogenous molecules and via reproductive hormones in the female sex organs. Activated MCs release a unique composition of preformed and newly synthesized bioactive molecules, like heparin, histamine, serotonin, proteolytic enzymes, cytokines, chemokines, and growth factors. MCs play important roles in immune responses, tissue remodeling, cell proliferation, angiogenesis, inflammation, wound healing, tissue homeostasis, health, and reproduction. As recently suggested, MCs enable perpetuation of the vertebrates because of key effects-spanning generations-in ovulation and pregnancy, as in life-preserving activities in inflammation and wound healing from birth till reproductive age, thus creating a permanent life-sustaining loop. Here, we present recent advances that further indicate that the MC is a specific life-supporting and progeny-safeguarding cell.

New perspectives on the origins and heterogeneity of mast cells

Mast cells are immune cells of the haematopoietic lineage that are now thought to have multifaceted functions during homeostasis and in various disease states. Furthermore, while mast cells have been known for a long time to contribute to allergic disease in adults, recent studies, mainly in mice, have highlighted their early origins during fetal development and potential for immune functions, including allergic responses, in early life. Our understanding of the imprinting of mast cells by particular tissues of residence and their potential for regulatory interactions with organ systems such as the peripheral immune, nervous and vascular systems is also rapidly evolving. Here, we discuss the origins of mast cells and their diverse and plastic phenotypes that are influenced by tissue residence. We explore how divergent phenotypes and functions might result from both their hard-wired 'nature' defined by their ontogeny and the 'nurture' they receive within specialized tissue microenvironments.

How "Neuronal" Are Human Skin Mast Cells?

Mast cells are evolutionarily old cells and the principal effectors in allergic responses and inflammation. They are seeded from the yolk sac during embryogenesis or are derived from hematopoietic progenitors and are therefore related to other leukocyte subsets, even though they form a separate clade in the hematopoietic system. Herein, we systematically bundle information from several recent high-throughput endeavors, especially those comparing MCs with other cell types, and combine such information with knowledge on the genes’ functions to reveal groups of neuronal markers specifically expressed by MCs. We focus on recent advances made regarding human tissue MCs, but also refer to studies in mice. In broad terms, genes hyper-expressed in MCs, but largely inactive in other myelocytes, can be classified into subcategories such as traffic/lysosomes (MLPH and RAB27B), the dopamine system (MAOB, DRD2, SLC6A3, and SLC18A2), Ca²⁺-related entities (CALB2), adhesion molecules (L1CAM and NTM) and, as an overall principle, the transcription factors and modulators of transcriptional activity (LMO4, PBX1, MEIS2, and EHMT2). Their function in MCs is generally unknown but may tentatively be deduced by comparison with other systems. MCs share functions with the nervous system, as they express typical neurotransmitters (histamine and serotonin) and a degranulation machinery that shares features with the neuronal apparatus at the synapse. Therefore, selective overlaps are plausible, and they further highlight the uniqueness of MCs within the myeloid system, as well as when compared with basophils. Apart from investigating their functional implications in MCs, a key question is whether their expression in the lineage is due to the specific reactivation of genes normally silenced in leukocytes or whether the genes are not switched off during mastocytic development from early progenitors.

Central nervous system regeneration in ascidians: cell migration and differentiation

Adult ascidians have the capacity to regenerate the central nervous system (CNS) and are therefore excellent models for studies on neuroregeneration. The possibility that undifferentiated blood cells are involved in adult neuroregeneration merits investigation. We analyzed the migration, circulation, and role of hemocytes of the ascidian Styela plicata in neuroregeneration. Hemocytes were removed and incubated with superparamagnetic iron oxide nanoparticles (SPION), and these SPION-labeled hemocytes were injected back into the animals (autologous transplant), followed by neurodegeneration with the neurotoxin 3-acetylpyridine (3AP). Magnetic resonance imaging showed that 1, 5, and 10 days after injury, hemocytes migrated to the intestinal region, siphons, and CNS. Immunohistochemistry revealed that the hemocytes that migrated to the CNS were putative stem cells (P-element-induced wimpy testis + or PIWI + cells). In the cortex of the neural ganglion, migrated hemocytes started to lose their PIWI labeling 5 days after injury, and 10 days later started to show β-III tubulin labeling. In the neural gland, however, the hemocytes remained undifferentiated during the entire experimental period. Transmission electron microscopy revealed regions in the neural gland with characteristics of neurogenic niches, not previously reported in ascidians. These results showed that migration of hemocytes to the hematopoietic tissue and to the 3AP-neurodegenerated region is central to the complex mechanism of neuroregeneration.

Ascidian (Chordata-Tunicata) Glycosaminoglycans: Extraction, Purification, Biochemical, and Spectroscopic Analysis

Sulfate polysaccharides with unique structures of the chondroitin/dermatan and heparin/heparan families of sulfated glycosaminoglycans have been described in several species of ascidians (Chordata-Tunicata). These unique sulfated glycans have been isolated from the ascidians and characterized by biochemical and spectroscopic methods. The ascidian glycans can be extracted by different tissues or cells by proteolytic digestion followed by cetylpyridinium chloride/ethanol precipitation. The total glycans are then fractionated by ion-exchange chromatography on DEAE-cellulose and/or Mono Q (HR 5/5) columns. Alternatively, precipitation with different ethanol concentrations can be employed. An initial analysis of the purified ascidian glycans is carried out by agarose gel electrophoresis on diaminopropane/acetate buffer, before or after digestion with specific glycosaminoglycan lyases or deaminative cleavage with nitrous acid. The disaccharides formed by exhaustive degradation of the glycans are purified by gel-filtration chromatography on a Superdex Peptide column and analyzed by HPLC on a strong ion-exchange Sax Spherisorb column. 1H- or 13C-nuclear magnetic resonance spectroscopy in one or two dimensions is used to confirm the structure of the intact glycans.

Mast Cells in Inflammation and Disease: Recent Progress and Ongoing Concerns

Mast cells have existed long before the development of adaptive immunity, although they have been given different names. Thus, in the marine urochordate Styela plicata, they have been designated as test cells. However, based on their morphological characteristics (including prominent cytoplasmic granules) and mediator content (including heparin, histamine, and neutral proteases), test cells are thought to represent members of the lineage known in vertebrates as mast cells. So this lineage presumably had important functions that preceded the development of antibodies, including IgE. Yet mast cells are best known, in humans, as key sources of mediators responsible for acute allergic reactions, notably including anaphylaxis, a severe and potentially fatal IgE-dependent immediate hypersensitivity reaction to apparently harmless antigens, including many found in foods and medicines. In this review, we briefly describe the origins of tissue mast cells and outline evidence that these cells can have beneficial as well as detrimental functions, both innately and as participants in adaptive immune responses. We also discuss aspects of mast cell heterogeneity and comment on how the plasticity of this lineage may provide insight into its roles in health and disease. Finally, we consider some currently open questions that are yet unresolved.

Multifaceted MRGPRX2: New insight into the role of mast cells in health and disease

Cutaneous mast cells (MCs) express Mas-related G protein-coupled receptor-X2 (MRGPRX2; mouse ortholog MrgprB2), which is activated by an ever-increasing number of cationic ligands. Antimicrobial host defense peptides (HDPs) generated by keratinocytes contribute to host defense likely by 2 mechanisms, one involving direct killing of microbes and the other via MC activation through MRGPRX2. However, its inappropriate activation may cause pseudoallergy and likely contribute to the pathogenesis of rosacea, atopic dermatitis, allergic contact dermatitis, urticaria, and mastocytosis. Gain- and loss-of-function missense single nucleotide polymorphisms in MRGPRX2 have been identified. The ability of certain ligands to serve as balanced or G protein-biased agonists has been defined. Small-molecule HDP mimetics that display both direct antimicrobial activity and activate MCs via MRGPRX2 have been developed. In addition, antibodies and reagents that modulate MRGPRX2 expression and signaling have been generated. In this article, we provide a comprehensive update on MrgprB2 and MRGPRX2 biology. We propose that harnessing MRGPRX2's host defense function by small-molecule HDP mimetics may provide a novel approach for the treatment of antibiotic-resistant cutaneous infections. In contrast, MRGPRX2-specific antibodies and inhibitors could be used for the modulation of allergic and inflammatory diseases that are mediated via this receptor.

Molecular Mechanisms of Mast Cell Activation by Cholesterol-Dependent Cytolysins

Mast cells are potent immune sensors of the tissue microenvironment. Within seconds of activation, they release various preformed biologically active products and initiate the process of de novo synthesis of cytokines, chemokines, and other inflammatory mediators. This process is regulated at multiple levels. Besides the extensively studied IgE and IgG receptors, toll-like receptors, MRGPR, and other protein receptor signaling pathways, there is a critical activation pathway based on cholesterol-dependent, pore-forming cytolytic exotoxins produced by Gram-positive bacterial pathogens. This pathway is initiated by binding the exotoxins to the cholesterol-rich membrane, followed by their dimerization, multimerization, pre-pore formation, and pore formation. At low sublytic concentrations, the exotoxins induce mast cell activation, including degranulation, intracellular calcium concentration changes, and transcriptional activation, resulting in production of cytokines and other inflammatory mediators. Higher toxin concentrations lead to cell death. Similar activation events are observed when mast cells are exposed to sublytic concentrations of saponins or some other compounds interfering with the membrane integrity. We review the molecular mechanisms of mast cell activation by pore-forming bacterial exotoxins, and other compounds inducing cholesterol-dependent plasma membrane perturbations. We discuss the importance of these signaling pathways in innate and acquired immunity.

Non-Anticoagulant Heparan Sulfate from the Ascidian Phallusia nigra Prevents Colon Carcinoma Metastasis in Mice by Disrupting Platelet-Tumor Cell Interaction

Although metastasis is the primary cause of death in patients with malignant solid tumors, efficient anti-metastatic therapies are not clinically available currently. Sulfated glycosaminoglycans from marine sources have shown promising pharmacological effects, acting on different steps of the metastatic process. Oversulfated dermatan sulfates from ascidians are effective in preventing metastasis by inhibition of P-selectin, a platelet surface protein involved in the platelet-tumor cell emboli formation. We report in this work that the heparan sulfate isolated from the viscera of the ascidian Phallusia nigra drastically attenuates metastases of colon carcinoma cells in mice. Our in vitro and in vivo assessments demonstrate that the P. nigra glycan has very low anticoagulant and antithrombotic activities and a reduced hypotension potential, although it efficiently prevented metastasis. Therefore, it may be a promising candidate for the development of a novel anti-metastatic drug.

Tunicate Heparan Sulfate Enriched in 2-Sulfated β-Glucuronic Acid: Structure, Anticoagulant Activity, and Inhibitory Effect on the Binding of Human Colon Adenocarcinoma Cells to Immobilized P-Selectin

Heparin or highly sulfated heparan sulfate (HS) has been described in different invertebrates. In ascidians (Chordata-Tunicata), these glycosaminoglycans occur in intracellular granules of oocyte accessory cells and circulating basophil-like cells, resembling mammalian mast cells and basophils, respectively. HS is also a component of the basement membrane of different ascidian organs. We have analyzed an HS isolated from the internal organs of the ascidian Phallusia nigra, using solution ¹H/¹³C NMR spectroscopy, which allowed us to identify and quantify the monosaccharides found in this glycosaminoglycan. A variety of α-glucosamine units with distinct degrees of sulfation and N-acetylation were revealed. The hexuronic acid units occur both as α-iduronic acid and β-glucuronic acid, with variable sulfation at the 2-position. A peculiar structural aspect of the tunicate HS is the high content of 2-sulfated β-glucuronic acid, which accounts for one-third of the total hexuronic acid units. Another distinct aspect of this HS is the occurrence of high content of N-acetylated α-glucosamine units bearing a sulfate group at position 6. The unique ascidian HS is a potent inhibitor of the binding of human colon adenocarcinoma cells to immobilized P-selectin, being 11-fold more potent than mammalian heparin, but almost ineffective as an anticoagulant. Thus, the components of the HS structure required to inhibit coagulation and binding of tumor cells to P-selectin are distinct. Our results also suggest that the regulation of the pathway involved in the biosynthesis of glycosaminoglycans suffered variations during the evolution of chordates.

Is it time for a new classification of mast cells? What do we know about mast cell heterogeneity?

Mast cells (MCs) are derived from committed precursors that leave the hematopoietic tissue, migrate in the blood, and colonize peripheral tissues where they terminally differentiate under microenvironment stimuli. They are distributed in almost all vascularized tissues where they act both as immune effectors and housekeeping cells, contributing to tissue homeostasis. Historically, MCs were classified into 2 subtypes, according to tryptic enzymes expression. However, MCs display a striking heterogeneity that reflects a complex interplay between different microenvironmental signals delivered by various tissues, and a differentiation program that decides their identity. Moreover, tissue-specific MCs show a trained memory, which contributes to shape their function in a specific microenvironment. In this review, we summarize the current state of our understanding of MC heterogeneity that reflects their different tissue experiences. We describe the discovery of unique cell molecules that can be used to distinguish specific MC subsets in vivo, and discuss how the improved ability to recognize these subsets provided new insights into the biology of MCs. These recent advances will be helpful for the understanding of the specific role of individual MC subsets in the control of tissue homeostasis, and in the regulation of pathological conditions such as infection, autoimmunity, and cancer.

Methods for Isolation and Characterization of Sulfated Glycosaminoglycans from Marine Invertebrates

Marine invertebrates produce different kinds of sulfated polysaccharides. These glycans play essential roles in several biological processes and the study of these molecules is promising in a variety of fields. In the following sections, we describe the materials and methods used for the extraction, purification, and characterization of marine invertebrate-derived glycosaminoglycans.

Marine glycosaminoglycan-like carbohydrates as potential drug candidates for infectious disease

Glycosaminoglycans (GAGs), present in the extracellular matrix, are exploited by numerous, distinct microbes for cellular attachment, adhesion, invasion and evasion of the host immune system. Glycosaminoglycans, including the widely used, clinical anticoagulant heparin and semi-synthetic analogues thereof, have been reported to inhibit and disrupt interactions between microbial proteins and carbohydrates present on the surface of host cells. However, the anticoagulant properties of unmodified, pharmaceutical heparin preparations preclude their capabilities as therapeutics for infectious disease states. Here, unique Glycosaminoglycan-like saccharides from various, distinct marine species are reported for their potential use as therapeutics against infectious diseases; many of which possess highly attenuated anticoagulant activities, while retaining significant antimicrobial properties.

Mast cell glycosaminoglycans

Mast cells contain granules packed with a mixture of proteins that are released on degranulation. The proteoglycan serglycin carries an array of glycosaminoglycan (GAG) side chains, sometimes heparin, sometimes chondroitin or dermatan sulphate. Tight packing of granule proteins is dependent on the presence of serglycin carrying these GAGs. The GAGs of mast cells were most intensively studied in the 1970s and 1980s, and though something is known about the fine structure of chondroitin sulphate and dermatan sulphate in mast cells, little is understood about the composition of the heparin/heparan sulphate chains. Recent emphasis on the analysis of mast cell heparin from different species and tissues, arising from the use of this GAG in medicine, lead to the question of whether variations within heparin structures between mast cell populations are as significant as variations in the mix of chondroitins and heparins.

Biological function of unique sulfated glycosaminoglycans in primitive chordates

Glycosaminoglycans with unique sulfation patterns have been identified in different species of ascidians (sea squirts), a group of marine invertebrates of the Phylum Chordata, sub-phylum Tunicata (or Urochordata). Oversulfated dermatan sulfate composed of [4-α-L-IdoA-(2-O-SO₃)^-1 → 3-β-D-GalNAc(4-OSO₃)^-1]_n repeating disaccharide units is found in the extracellular matrix of several organs, where it seems to interact with collagen fibers. This dermatan sulfate co-localizes with a decorin-like protein, as indicated by immunohistochemical analysis. Low sulfated heparin/heparan sulfate-like glycans composed mainly of [4-α-L-IdoA-(2-OSO₃)^-1 → 4-α-D-GlcN(SO₃)^-1 (6-O-SO₃)^-1]_n and [4-α-L-IdoA-(2-O-SO₃)^-1 → 4-α-D-GlcN(SO₃)^-1]_n have also been described in ascidians. These heparin-like glycans occur in intracellular granules of oocyte assessory cells, named test cells, in circulating basophil-like cells in the hemolymph, and at the basement membrane of different ascidian organs. In this review, we present an overview of the structure, distribution, extracellular and intracellular localization of the sulfated glycosaminoglycans in different species and tissues of ascidians. Considering the phylogenetic position of the subphylum Tunicata in the phylum Chordata, a careful analysis of these data can reveal important information about how these glycans evolved from invertebrate to vertebrate animals.

Ascidian bioresources: common and variant chemical compositions and exploitation strategy - examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalis

To explore abundant marine ascidian bioresources, four species from two orders have been compared in their chemical compositions. After a universal separation of the animal body into two fractions, all tunics have been found rich in carbohydrate contents, while all inner body tissues are richer in proteins. Cellulose is present almost exclusively in the tunics and more in the order Stolidobranchia, while more sulfated polysaccharides are present in Phlebobranchia species. Almost all proteins are collagens with a high essential amino acid index and high delicious amino acid (DAA) content. All fractions also have high contents of good-quality fatty acids and trace minerals but low toxic element contents, with different sterols and glycosaminoglycans. There are species-specific characteristics observed for vanadium accumulation and sterol structures which are also meaningful for ascidian chemotaxonomy and resource exploitation. It is suggested that in addition to the present utilizations of tunics for cellulose production and of some species' inner body tissues as human food, one should explore all species' inner body tissues as human foods and all tunics as food or animal feed with the contained cellulose as dietary fiber. Collagens, sulfated polysaccharides, glycosaminoglycans, sterols and trace elements could be explored as byproducts for, e.g. pharmaceutical and chemical industries.

Expression profiling of constitutive mast cells reveals a unique identity within the immune system

Mast cells are evolutionarily ancient sentinel cells. Like basophils, mast cells express the high-affinity receptor for immunoglobulin E (IgE) and have been linked to host defense and diverse immune-system-mediated diseases. To better characterize the function of these cells, we assessed the transcriptional profiles of mast cells isolated from peripheral connective tissues and basophils isolated from spleen and blood. We found that mast cells were transcriptionally distinct, clustering independently from all other profiled cells, and that mast cells demonstrated considerably greater heterogeneity across tissues than previously appreciated. We observed minimal homology between mast cells and basophils, which shared more overlap with other circulating granulocytes than with mast cells. The derivation of mast-cell and basophil transcriptional signatures underscores their differential capacities to detect environmental signals and influence the inflammatory milieu.

Ascidian (Chordata-Tunicata) glycosaminoglycans: extraction, purification, biochemical, and spectroscopic analysis

Sulfated polysaccharides with unique structures of the chondroitin/dermatan and heparin/heparan families of sulfated glycosaminoglycans have been described in several species of ascidians (Chordata-Tunicata). These unique sulfated glycans have been isolated from-ascidians and characterized by biochemical and spectroscopic methods. The ascidian glycans can be extracted by different tissues or cells by proteolytic digestion followed by cetylpyridinium chloride/ethanol precipitation. The total glycans are then fractionated by ion-exchange chromatography on DEAE-cellulose and/or Mono Q (HR 5/5) columns. Alternatively, precipitation with different ethanol concentrations can be employed. An initial analysis of the purified ascidian glycans is carried out by agarose gel electrophoresis on diaminopropane/acetate buffer, before or after digestion with specific glycosaminoglycan lyases or deaminative cleavage with nitrous acid. The disaccharides formed by exhaustive degradation of the glycans is purified by gel-filtration chromatography on a Superdex-peptide column and analyzed by HPLC on a strong ion exchange Sax-Spherisorb column. 1H or 13C nuclear magnetic resonance spectroscopy in one or two dimensions is used to confirm the structure of the intact glycans.

The phylogenetic profile of mast cells

Mast cells (MCs) are tissue-based immune cells that participate to both innate and adaptive immunities as well as to tissue-remodelling processes. Their evolutionary history appears as a fascinating process, whose outline we can only partly reconstruct according to current remnant evidence. MCs have been identified in all vertebrate classes, and a cell population with the overall characteristics of higher vertebrate MCs is identifiable even in the most evolutionarily advanced fish species. In invertebrates, cells related to vertebrate MCs have been recognized in ascidians, a class of urochordates which appeared approximately 500 million years ago. These comprise the granular hemocyte with intermediate characteristics of basophils and MCs and the "test cell" (see below). Both types of cells contain histamine and heparin, and provide defensive functions. The test cell releases tryptase after stimulation with compound 48/80. A leukocyte ancestor operating in the context of a primitive local innate immunity probably represents the MC phylogenetic progenitor. This cell was likely involved in phagocytic and killing activity against pathogens and operated as a general inducer of inflammation. This early type of defensive cell possibly expressed concomitant tissue-reparative functions. With the advent of recombinase activating gene (RAG)-mediated adaptive immunity in the Cambrian era, some 550 million years ago, and the emergence of early vertebrates, MC progenitors differentiated towards a more complex cellular entity. Early MCs probably appeared in the last common ancestor we shared with hagfish, lamprey, and sharks about 450-500 million years ago.

Histamine regulates the inflammatory response of the tunicate Styela plicata

Histamine is stored inside hemocytes of the tunicate Styela plicata (Chordata, Tunicata, Ascidiacea), but no evidence on its role in the regulation of the immune response of this species has been reported. We examined whether histamine participated in the regulation of inflammation and host defense in S. plicata. The presence of histamine inside S. plicata hemocytes was confirmed by flow cytometry, and histamine release was detected by ELISA, after in vitro hemocyte stimulation with different PAMPs. In vitro hemocyte treatment with histamine, or specific histamine-receptor agonists, reduced their phagocytic ability. Injection of histamine into the tunic recruited hemocytes to the site of injection. Systemic injection of histamine, or the histamine-releasing agent compound 48/80, decreased the phagocytic ability of hemocytes. Histamine promoted the constriction of tunic hemolymph vessels in vivo, having a direct effect on vasoconstriction in tunic explants. These results provide for the first time clear evidence for the involvement of histamine in the regulation of inflammation and host defense in tunicates.

Glycosaminoglycans analogs from marine invertebrates: structure, biological effects, and potential as new therapeutics

In this review, several glycosaminoglycan analogs obtained from different marine invertebrate are reported. The structure, biological activity and mechanism of action of these unique molecules are detailed reviewed and exemplified by experiments in vitro and in vivo. Among the glycans studied are low-sulfated heparin-like polymers from ascidians, containing significant anticoagulant activity and no bleeding effect; dermatan sulfates with significant neurite outgrowth promoting activity and anti-P-selectin from ascidians, and a unique fucosylated chondroitin sulfate from sea cucumbers, possessing anticoagulant activity after oral administration and high anti P- and L-selectin activities. The therapeutic value and safety of these invertebrate glycans have been extensively proved by several experimental animal models of diseases, including thrombosis, inflammation and metastasis. These invertebrate glycans can be obtained in high concentrations from marine organisms that have been used as a food source for decades, and usually obtained from marine farms in sufficient quantities to be used as starting material for new therapeutics.

The progress and promise of zebrafish as a model to study mast cells

Immunological and hematological research using the zebrafish (Danio rerio) has significantly advanced our understanding of blood lineage ontology, cellular functions and mechanisms, and provided opportunities for disease modeling. Mast cells are an immunological cell type involved in innate and adaptive immune systems, hypersensitivity reactions and cancer progression. The application of zebrafish to study mast cell biology exploits the developmental and imaging opportunities inherent in this model system to enable detailed genetic and molecular studies of this lineage outside of traditional mammalian models. In this review, we first place the importance of mast cell research in zebrafish into the context of comparative studies of mast cells in other fish species and highlight its advantages due to superior experimental tractability and direct visualization in transparent embryos. We discuss current and future tools for mast cell research in zebrafish and the notable results of using zebrafish for understanding mast cell fate determination and our development of a systemic mastocytosis model.

Ancient origin of mast cells

The sentinel roles of mammalian mast cells (MCs) in varied infections raised the question of their evolutionary origin. We discovered that the test cells in the sea squirt Ciona intestinalis morphologically and histochemically resembled cutaneous human MCs. Like the latter, C. intestinalis test cells stored histamine and varied heparin·serine protease complexes in their granules. Moreover, they exocytosed these preformed mediators when exposed to compound 48/80. In support of the histamine data, a C. intestinalis-derived cDNA was isolated that resembled that which encodes histidine decarboxylase in human MCs. Like heparin-expressing mammalian MCs, activated test cells produced prostaglandin D2 and contained cDNAs that encode a protein that resembles the synthase needed for its biosynthesis in human MCs. The accumulated morphological, histochemical, biochemical, and molecular biology data suggest that the test cells in C. intestinalis are the counterparts of mammalian MCs that reside in varied connective tissues. The accumulated data point to an ancient origin of MCs that predates the emergence of the chordates >500million years ago, well before the development of adaptive immunity. The remarkable conservation of MCs throughout evolution is consistent with their importance in innate immunity.

A heparin-like compound isolated from a marine crab rich in glucuronic acid 2-O-sulfate presents low anticoagulant activity

A natural heparin-like compound isolated from the crab Goniopsis cruentata was structurally characterized and its anticoagulant and hemorrhagic activities were determined. Enzymatic and nuclear magnetic resonance analysis revealed that its structure is rich in disulfated disaccharides, possessing significant amounts of 2-O-sulfated-β-D-glucuronic acid units. Furthermore, low amounts of trisulfated disaccharide units containing 2-O-sulfated-α-L-iduronic acid were detected, when compared to mammalian heparin. In addition, this heparin-like structure showed negligible in vitro anticoagulant activity and low bleeding potency, facts that make it a suitable candidate for the development of structure-driven, heparin based therapeutic agents with fewer undesirable effects.

Structure and physicochemical characterisation of heparin

Heparin is a member of the heparan sulphate family of glycosaminoglycans, a linear polysaccharide with a complex sequence resulting from the action of post-polymerisation enzymes on a regular repeating disaccharide background. Its overall conformation is rod-like in solution as well as in the solid state, but the conformational fluctuations of iduronate residues give rise to considerable internal motion and variation in local three-dimensional structure. Structure/function relationships and their relation to sequence are still the subject of argument, but new methodologies to tackle the subject are emerging. Heparin as a therapeutic agent and as the object of research may be characterised by numerous physico-chemical techniques. These include chromatographic methods for measurement of molecular weight; a variety of spectroscopic techniques; separation methods for whole polysaccharides, as well as for oligo- and monosaccharides; and mass spectrometric methods for mapping and sequence analysis. The impetus provided by the discovery of heparin contamination with oversulphated chondroitin sulphate has been influential in bringing combinations of many old and new techniques into use to ensure that heparin is sufficiently consistent and pure to be used safely. Synthetic and semi-synthetic heparins are in development and may become reality in the relatively near future.

Mast cells as cellular sensors in inflammation and immunity

Mast cells are localized in tissues. Intense research on these cells over the years has demonstrated their role as effector cells in the maintenance of tissue integrity following injury produced by infectious agents, toxins, metabolic states, etc. After stimulation they release a sophisticated array of inflammatory mediators, cytokines, and growth factors to orchestrate an inflammatory response. These mediators can directly initiate tissue responses on resident cells, but they have also been shown to regulate other infiltrating immune cell functions. Research in recent years has revealed that the outcome of mast cell actions is not always detrimental for the host but can also limit disease development. In addition, mast cell functions highly depend on the physiological context in the organism. Depending on the genetic background, strength of the injurious event, the particular microenvironment, mast cells direct responses ranging from pro- to anti-inflammatory. It appears that they have evolved as cellular sensors to discern their environment in order to initiate an appropriate physiological response either aimed to favor inflammation for repair or at the contrary limit the inflammatory process to prevent further damage. Like every sophisticated machinery, its dysregulation leads to pathology. Given the broad distribution of mast cells in tissues this also explains their implication in many inflammatory diseases.

Evolution of glycosaminoglycans: Comparative biochemical study

Glycosaminoglycans, a major component of the extracellular matrix molecules in animal tissues, play important roles in various physiological events. Glycosaminoglycans are found in not only vertebrates but also many invertebrates, implying a conserved function in the animal kingdom. Here, we discuss the analysis of glycosaminoglycans in 11 invertebrate phyla focusing on structure as well as physiological functions elucidated in model organisms. Various sulfated structures of heparan sulfate are widely distributed from very primitive organisms to humans, indicating an involvement in fundamental biological processes. By contrast, chondroitin/dermatan sulfate from lower organisms is limited in its structural complexity and often associated with a particular function. The presence of hyaluronic acid outside of vertebrates has been reported only in a mollusk.

The history of the controversial relationship between mast cells and basophils

Work on mast cells and basophils began with their identification by Paul Ehrlich at the end of the 19th century. Mast cells and basophils were immediately perceived as closely linked cells and early nomenclature formulated by Ehrlich himself, i.e., tissue "Mastzellen" and blood "Mastzellen", reflected this unifying viewpoint. With time, important functional affinities but also substantial diversities were recognized. This review article focuses on the historical development of the concept of mast cell/basophil specificity, from the initial identification of these cells to current studies.

Evidence for the heparin-binding ability of the ascidian Xlink domain and insight into the evolution of the Xlink domain in chordates

The vertebrate Xlink domain is found in two types of genes: lecticans and their associated hyaluronan-and-proteoglycan-binding-link-proteins (HAPLNs), which are components of the extracellular matrix, and those represented by CD44 and stabilins, which are expressed on the surface of lymphocytes. In both types of genes, Xlink functions as a hyaluronan binding domain. We have already reported that protochordate ascidians possess only the latter type of gene. The present analysis of the expression of ascidian Xlink domain genes revealed that these genes function in blood cell migration and apoptosis. While the Xlink domain is found in various metazoans, including ascidians and nematodes, hyaluronan is believed to be specific for vertebrates. In comprehensive genome surveys for hyaluronan synthase (HAS), we found no HAS gene in ascidians. We also established that hyaluronan is absent from the ascidian body biochemically. Therefore, ascidians possess the Xlink domain, but they lack HA. We recovered one ascidian Xlink domain gene that encoded a heparin-binding protein, although it shows no affinity for hyaluronan. Based on these findings, we conclude that in invertebrates, the Xlink domain serves as heparin-binding protein domain and functions in blood cell migration and apoptosis. Its binding affinity for HA might have been acquired in the vertebrate lineage.

Unique extracellular matrix heparan sulfate from the bivalve Nodipecten nodosus (Linnaeus, 1758) safely inhibits arterial thrombosis after photochemically induced endothelial lesion

Heparin-like glycans with diverse disaccharide composition and high anticoagulant activity have been described in several families of marine mollusks. The present work focused on the structural characterization of a new heparan sulfate (HS)-like polymer isolated from the mollusk Nodipecten nodosus (Linnaeus, 1758) and on its anticoagulant and antithrombotic properties. Total glycans were extracted from the mollusk and fractionated by ethanol precipitation. The main component (>90%) was identified as HS-like glycosaminoglycan, representing approximately 4.6 mg g(-1) of dry tissue. The mollusk HS resists degradation with heparinase I but is cleaved by nitrous acid. Analysis of the mollusk glycan by one-dimensional (1)H, two-dimensional correlated spectroscopy, and heteronuclear single quantum coherence nuclear magnetic resonance revealed characteristic signals of glucuronic acid and glucosamine residues. Signals corresponding to anomeric protons of nonsulfated, 3- or 2-sulfated glucuronic acid as well as N-sulfated and/or 6-sulfated glucosamine were also observed. The mollusk HS has an anticoagulant activity of 36 IU mg(-1), 5-fold lower than porcine heparin (180 IU mg(-1)), as measured by the activated partial thromboplastin time assay. It also inhibits factor Xa (IC(50) = 0.835 microg ml(-1)) and thrombin (IC(50) = 9.3 microg ml(-1)) in the presence of antithrombin. In vivo assays demonstrated that at the dose of 1 mg kg(-1), the mollusk HS inhibited thrombus growth in photochemically injured arteries. No bleeding effect, factor XIIa-mediated kallikrein activity, or toxic effect on fibroblast cells was induced by the invertebrate HS at the antithrombotic dose.

The mast cell: an evolutionary perspective

This review article is an attempt to trace the evolution of mast cells (MCs). These immune cells have been identified in all vertebrate classes as single-lobed cells containing variable amounts of membrane-bound secretory granules which store a large series of mediators, namely histamine, proteases, cytokines and growth factors. Other MC features, at least in mammals, are the c-kit receptor for the stem cell factor and the high-affinity receptor, FcepsilonRI, for immunoglobulin E (IgE). The c-kit receptor also has been identified in fish MCs. The FcepsilonRI receptor seems to be a more recent acquisition in MC phylogenesis given that IgE originated in mammalian species. Tryptase and histamine have also been recognized in MCs of teleost fish. Thus, a cell population with the overall characteristics of higher vertebrate MCs is identifiable in the most evolutionarily advanced fish species. Two potential MC progenitors have been identified in ascidians (urochordates which appeared approximately 500 million years ago): the basophil/MC-like granular haemocyte and the test cell. Both contain histamine and heparin, and provide defensive functions. Some granular haemocytes in Arthropoda also closely approximate the ultrastructure of modern MCs. The origin of MCs is probably to be found in a leukocyte ancestor operating in the context of a primitive local innate immunity and involved in phagocytic and killing activity against pathogens. From this type of defensive cell, the MC phylogenetic progenitor evolved into a tissue regulatory and remodelling cell, which was incorporated into the networks of recombinase activating genes (RAG)-mediated adaptive immunity in the Cambrian era, some 550 million years ago. Early MCs probably appeared in the last common ancestor we shared with hagfish, lamprey and sharks about 450-500 million years ago.

Our perception of the mast cell from Paul Ehrlich to now

Just over a century ago Paul Ehrlich received the Nobel Prize for his studies of immunity. This review describes one of his legacies, the histochemical description of the mast cell, and the research that has ensued since then. After a long period of largely descriptive studies, which revealed little about the biological role of the mast cell, the field was galvanized in the 1950s by the recognition that the mast cell was the main repository of histamine and a key participant in anaphylactic reactions. Although the mast cell was long-viewed in these terms, recent research has now shown that the mast cell also plays a key role in innate and adaptive immune responses, autoimmune disease, and possibly tissue homeostasis by virtue of its expression of a diverse array of receptors and biologically active products. In addition, the responsiveness of mast cells to immunological and pathological stimulants is highly modulated by the tissue cytokine environment and by synergistic, or inhibitory, interactions among the various mast cell receptor systems. This once enigmatic cell of Paul Ehrlich has proved to be both adaptable and multifunctional.

Urochordate histoincompatible interactions activate vertebrate-like coagulation system components

The colonial ascidian Botryllus schlosseri expresses a unique allorecognition system. When two histoincompatible Botryllus colonies come into direct contact, they develop an inflammatory-like rejection response. A surprising high number of vertebrates' coagulation genes and coagulation-related domains were disclosed in a cDNA library of differentially expressed sequence tags (ESTs), prepared for this allorejection process. Serine proteases, especially from the trypsin family, were highly represented among Botryllus library ortholgues and its “molecular function” gene ontology analysis. These, together with the built-up clot-like lesions in the interaction area, led us to further test whether a vertebrate-like clotting system participates in Botryllus innate immunity. Three morphologically distinct clot types (points of rejection; POR) were followed. We demonstrated the specific expression of nine coagulation orthologue transcripts in Botryllus rejection processes and effects of the anti-coagulant heparin on POR formation and heartbeats. In situ hybridization of fibrinogen and von Willebrand factor orthologues elucidated enhanced expression patterns specific to histoincompatible reactions as well as common expressions not augmented by innate immunity. Immunohistochemistry for fibrinogen revealed, in naïve and immune challenged colonies alike, specific antibody binding to a small population of Botryllus compartment cells. Altogether, molecular, physiological and morphological outcomes suggest the involvement of vertebrates-like coagulation elements in urochordate immunity, not assigned with vasculature injury.

Mast cells and mastocytosis

Mast cells have been recognized for well over 100 years. With time, human mast cells have been documented to originate from CD34+ cells, and have been implicated in host responses in both innate and acquired immunity. In clinical immunology, they are recognized for their central role in IgE-mediated degranulation and allergic inflammation by virtue of their expression of the high-affinity receptor for IgE and release of potent proinflammatory mediators. In hematology, the clinical disease of mastocytosis is characterized by a pathologic increase of mast cells in tissues, often associated with mutations in KIT, the receptor for stem cell factor. More recently, and with increased understanding of how human mast cells are activated through receptors including the high-affinity receptor for IgE and KIT, specific tyrosine kinase inhibitors have been identified with the potential to interrupt signaling pathways and thus limit the proliferation of mast cells as well as their activation through immunoglobulin receptors.

Toxicity and biodegradation of the LAS surfactant 1-(p-sulfophenyl)nonane in presence of the ascidian Styela plicata

The main objective of this study, within development of engineering solutions for coastal areas depuration, was to establish the role of the benthic macro-organisms in the biodegradation of the detergents in marine environment and to estimate the toxicity of these substances for a particular marine species: the ascidian Styela plicata. The experimental studies undertaken in aquarium with seawater enriched in a pure lynear alkylbenzene sulfonate (LAS), the 1-(p-sulfophenyl)nonane (1C9-LAS), showed that the degradation was two times more fast in presence of the S. plicata, than of the only marine bacteria. The toxicity of this pollutant was also determined. This study demonstrates that the ascidia S. plicata can be a potential biomediator for the surfactant 1C9-LAS, and it can be used to design a pilot project, to bioremediate harbours and the coastal areas interested from the urban pollution.

In vivo antithrombotic properties of a heparin from the oocyte test cells of the sea squirt Styela plicata(Chordata-Tunicata)

In the ascidian Styela plicata, the oocytes are surrounded by two types of accessory cells named follicle cells and test cells. A heparin-like substance with an anticoagulant activity equivalent to 10% of mammalian heparin and about 5% as potent as the mammalian counterpart for the inhibition of thrombin by antithrombin was isolated from the oocyte test cells. In the present study, we compared the antithrombotic and hemorrhagic effects of sea squirt oocyte test cell heparin with those of porcine heparin in rat models of venous thrombosis and blood loss. Intravenous administration of the oocyte test cell heparin to Wistar rats (both sexes, weighing approximately 300 g, N = 4 in each group) at a dose of 5.0 mg/kg body weight, which produced a 1.8-fold increase in plasma activated partial thromboplastin time, inhibited thrombosis by 45 +/- 13.5% (mean +/- SD) without any bleeding effect. The same dose of porcine heparin inhibited thrombosis by 100 +/- 1.4%, but produced a blood loss three times greater than that of the saline-treated control. However, 10-fold reduction of the dose of porcine heparin to 0.5 mg/kg body weight, which produced a 5-fold increase in plasma-activated partial thromboplastin time, inhibited thrombosis by 70 +/- 13% without any bleeding effect. The antithrombotic properties of a new heparin isolated from test cells of the sea squirt S. plicata, reported here for the first time, indicate that, although sea squirt oocyte test cell heparin was a poor anticoagulant compared to porcine heparin, it had a significant antithrombotic effect without causing bleeding.

Isolation and characterization of a heparin with low antithrombin activity from the body of Styela plicata (Chordata-Tunicata). Distinct effects on venous and arterial models of thrombosis

INTRODUCTION

A heparin preparation with low antithrombin activity and different disaccharide composition than mammalian heparin was isolated from the body of the ascidian Styela plicata (Chordata-Tunicata). The disaccharide composition and the effect of the invertebrate glycan on venous and arterial models of thrombosis was investigated.

METHODS AND RESULTS

High performance liquid chromatography of the products formed by a mixture of heparin lyases showed that the ascidian heparin is composed mainly by delta UA(2SO4)-1-->4-beta-d-GlcN(SO4) (47.5%), delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(6SO4) (38.3%) disaccharides and smaller amounts of the disaccharides delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4)(6SO4) (2.8%) and delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4) (8.0%). The invertebrate heparin has an aPTT activity of 18 IU/mg and an antithrombin-mediated antithrombin and anti-factor Xa activities 10-fold lower than that of mammalian heparin. In a venous model of thrombosis in the vena cava, S. plicata heparin inhibits only 80% of thrombosis at a dose 10-fold higher than that of the mammalian heparin that inhibits 100% of thrombosis. However, in an arterio-shunt model of arterial thrombosis, both S. plicata and mammalian heparin possess equivalent antithrombotic activities. It is also shown that at equivalent doses, ascidian heparin has a lower bleeding effect than mammalian heparin.

CONCLUSION

The antithrombin-mediated anticoagulant activity of heparin polymers is not directly related to antithrombotic potency in the arterio-venous shunt. The results of the present work suggest that heparin preparations obtained from the body of S. plicata may have a safer therapeutic action in the treatment of arterial thrombosis than mammalian heparin.

The Hemolymph of the Ascidian Styela plicata (Chordata-Tunicata) Contains Heparin inside Basophil-like Cells and a Unique Sulfated Galactoglucan in the Plasma

The hemolymph of ascidians (Chordata-Tunicata) contains different types of hemocytes embedded in a liquid plasma. In the present study, heparin and a sulfated heteropolysaccharide were purified from the hemolymph of the ascidian Styela plicata. The heteropolysaccharide occurs free in the plasma, is composed of glucose ( approximately 60%) and galactose ( approximately 40%), and is highly sulfated. Heparin, on the other hand, occurs in the hemocytes, and high performance liquid chromatography of the products formed by degradation with specific lyases revealed that it is composed mainly by the disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4)) (39.7%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(6SO(4)) (38.2%). Small amounts of the 3-O-sulfated disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4)) (9.8%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4))(6SO(4)) (3.8%) were also detected. These 3-O-sulfated disaccharides were demonstrated to be essential for the binding of the hemocyte heparin to antithrombin III. Electron microscopy techniques were used to characterize the ultrastructure of the hemocytes and to localize heparin and histamine in these cells. At least five cell types were recognized and classified as univacuolated and multivacuolated cells, amebocytes, hemoblasts, and granulocytes. Immunocytochemistry showed that heparin and histamine co-localize in intracellular granules of only one type of hemocyte, the granulocyte. These results show for the first time that in ascidians, a sulfated galactoglucan circulates free in the plasma, and heparin occurs as an intracellular product of a circulating basophil-like cell.

Placental dermatan sulfate: isolation, anticoagulant activity, and association with heparin cofactor II

Pregnancy is associated with hemostatic challenges that may lead to thrombosis. Heparin cofactor II (HCII) is a glycosaminoglycan-dependent thrombin inhibitor present in both maternal and fetal plasma. HCII activity increases during pregnancy, and HCII levels are significantly decreased in women with severe pre-eclampsia. Dermatan sulfate (DS) specifically activates HCII and is abundant in the placenta, but the locations of DS and HCII in the placenta have not been determined. We present evidence that DS is the major anticoagulant glycosaminoglycan in the human placenta at term. DS isolated from human placenta contains disaccharides implicated in activation of HCII and has anticoagulant activity similar to that of mucosal DS. Immunohistochemical studies revealed that DS is associated with fetal blood vessels and stromal regions of placental villi but is notably absent from the syncytiotrophoblast cells in contact with the maternal circulation. HCII colocalizes with DS in the walls of fetal blood vessels and is also present in syncytiotrophoblast cells. Our data suggest that DS is in a position to activate HCII in the fetal blood vessels or in the stroma of placental villi after injury to the syncytiotrophoblast layer and thereby inhibit fibrin generation in the placenta.

Antithrombin-mediated anticoagulant activity of sulfated polysaccharides: different mechanisms for heparin and sulfated galactans

We investigated the mechanisms of anticoagulant activity mediated by sulfated galactans. The anticoagulant activity of sulfated polysaccharides is achieved mainly through potentiation of plasma cofactors, which are the natural inhibitors of coagulation proteases. Our results indicated the following. 1) Structural requirements for the interaction of sulfated galactans with coagulation inhibitors and their target proteases are not merely a consequence of their charge density. 2) The structural basis of this interaction is complex because it involves naturally heterogeneous polysaccharides but depends on the distribution of sulfate groups and on monosaccharide composition. 3) Sulfated galactans require significantly longer chains than heparin to achieve anticoagulant activity. 4) Possibly, it is the bulk structure of the sulfated galactan, and not a specific minor component as in heparin, that determines its interaction with antithrombin. 5) Sulfated galactans of approximately 15 to approximately 45 kDa bind to antithrombin but are unable to link the plasma inhibitor and thrombin. This last effect requires a molecular size above 45 kDa. 6) Sulfated galactan and heparin bind to different sites on antithrombin. 7) Sulfated galactans are less effective than heparin at promoting antithrombin conformational activation. Overall, these observations indicate that a different mechanism predominates over the conformational activation of antithrombin in ensuring the antithrombin-mediated anticoagulant activity of the sulfated galactans. Possibly, sulfated galactan connects antithrombin and thrombin, holding the protease in an inactive form. The conformational activation of antithrombin and the consequent formation of a covalent complex with thrombin appear to be less important for the anticoagulant activity of sulfated galactan than for heparin. Our results demonstrate that the paradigm of heparin-antithrombin interaction cannot be extended to other sulfated polysaccharides. Each type of polysaccharide may form a particular complex with the plasma inhibitor and the target protease.