Neuronal cell adhesion, mediated by the heparin-binding neuroregulatory factor midkine, is specifically inhibited by chondroitin sulfate E. Structural ans functional implications of the over-sulfated chondroitin sulfate

Midkine is upregulated in the hippocampus following both spatial and olfactory reward association learning and enhances memory

Hippocampal neuronal plasticity is a fundamental process underpinning learning and memory formation and requiring elaborate molecular mechanisms that result in the dynamic remodelling of synaptic connectivity. The neurotrophic properties of midkine (Mdk) have been implicated in the development and repair of the nervous system, while Mdk knockout resulted in deficits in the formation of certain types of memory. The role of Mdk in the process of memory-associated neuronal plasticity, however, remains poorly understood. We investigated the learning-induced regulation of Mdk in spatial navigation and association learning using the water maze and the odour reward association learning paradigms, characterising a temporal profile of Mdk protein expression post-learning. Both learning events revealed similar patterns of upregulation of expression of the protein in the rat hippocampal dentate gyrus, which were rapid and transient. Moreover, administration of recombinant Mdk during the endogenous Mdk upregulation following learning enhanced memory in the water maze task revealing a pro-cognitive action of Mdk. We further show that, within the adult hippocampus, Mdk mRNA is predominantly expressed in granular and pyramidal neurons and that hippocampal neuronal Mdk expression is regulated by the canonical plasticity-associated neurotransmitter glutamate. Finally, we confirm that the positive action of Mdk on neurite outgrowth previously noted in cortical and cerebellar neurons extends to hippocampal neurons. Together, our findings suggest a role for Mdk in glutamate-mediated hippocampal neuronal plasticity important for long-term memory consolidation.

Neuritogenic glycosaminoglycan hydrogels promote functional recovery after severe traumatic brain injury

Objective.Severe traumatic brain injury (sTBI) induced neuronal loss and brain atrophy contribute significantly to long-term disabilities. Brain extracellular matrix (ECM) associated chondroitin sulfate (CS) glycosaminoglycans promote neural stem cell (NSC) maintenance, and CS hydrogel implants have demonstrated the ability to enhance neuroprotection, in preclinical sTBI studies. However, the ability of neuritogenic chimeric peptide (CP) functionalized CS hydrogels in promoting functional recovery, after controlled cortical impact (CCI) and suction ablation (SA) induced sTBI, has not been previously demonstrated. We hypothesized that neuritogenic (CS)CP hydrogels will promote neuritogenesis of human NSCs, and accelerate brain tissue repair and functional recovery in sTBI rats.Approach.We synthesized chondroitin 4-Osulfate (CS-A)CP, and 4,6-O-sulfate (CS-E)CP hydrogels, using strain promoted azide-alkyne cycloaddition (SPAAC), to promote cell adhesion and neuritogenesis of human NSCs,in vitro; and assessed the ability of (CS-A)CP hydrogels in promoting tissue and functional repair, in a novel CCI-SA sTBI model,in vivo. Main results.Results indicated that (CS-E)CP hydrogels significantly enhanced human NSC aggregation and migration via focal adhesion kinase complexes, when compared to NSCs in (CS-A)CP hydrogels,in vitro. In contrast, NSCs encapsulated in (CS-A)CP hydrogels differentiated into neurons bearing longer neurites and showed greater spontaneous activity, when compared to those in (CS-E)CP hydrogels. The intracavitary implantation of (CS-A)CP hydrogels, acutely after CCI-SA-sTBI, prevented neuronal and axonal loss, as determined by immunohistochemical analyses. (CS-A)CP hydrogel implanted animals also demonstrated the significantly accelerated recovery of 'reach-to-grasp' function when compared to sTBI controls, over a period of 5-weeks.Significance.These findings demonstrate the neuritogenic and neuroprotective attributes of (CS)CP 'click' hydrogels, and open new avenues for the development of multifunctional glycomaterials that are functionalized with biorthogonal handles for sTBI repair.

Recent progress in marine chondroitin sulfate, dermatan sulfate, and chondroitin sulfate/dermatan sulfate hybrid chains as potential functional foods and therapeutic agents

Chondroitin sulfate (CS), dermatan sulfate (DS), and CS/DS hybrid chains are natural complex glycosaminoglycans with high structural diversity and widely distributed in marine organisms, such as fish, shrimp, starfish, and sea cucumber. Numerous CS, DS, and CS/DS hybrid chains with various structures and activities have been obtained from marine animals and have received extensive attention. However, only a few of these hybrid chains have been well-characterized and commercially developed. This review presents information on the extraction, purification, structural characterization, biological activities, potential action mechanisms, and structure-activity relationships of marine CS, DS, and CS/DS hybrid chains. We also discuss the challenges and perspectives in the research of CS, DS, and CS/DS hybrid chains. This review may provide a useful reference for the further investigation, development, and application of CS, DS, and CS/DS hybrid chains in the fields of functional foods and therapeutic agents.

Midkine-A novel player in cardiovascular diseases

Midkine (MK) is a 13-kDa heparin-binding cytokine and growth factor with anti-apoptotic, pro-angiogenic, pro-inflammatory and anti-infective functions, that enable it to partake in a series of physiological and pathophysiological processes. In the past, research revolving around MK has concentrated on its roles in reproduction and development, tissue protection and repair as well as inflammatory and malignant processes. In the recent few years, MK's implication in a wide scope of cardiovascular diseases has been rigorously investigated. Nonetheless, there is still no broadly accepted consensus on whether MK exerts generally detrimental or favorable effects in cardiovascular diseases. The truth probably resides somewhere in-between and depends on the underlying physiological or pathophysiological condition. It is therefore crucial to thoroughly examine and appraise MK's participation in cardiovascular diseases. In this review, we introduce the MK gene and protein, its multiple receptors and signaling pathways along with its expression in the vascular system and its most substantial functions in cardiovascular biology. Further, we recapitulate the current evidence of MK's expression in cardiovascular diseases, addressing the various sources and modes of MK expression. Moreover, we summarize the most significant implications of MK in cardiovascular diseases with particular emphasis on MK's advantageous and injurious functions, highlighting its ample diagnostic and therapeutic potential. Also, we focus on conflicting roles of MK in a number of cardiovascular diseases and try to provide some clarity and guidance to MK's multifaceted roles. In summary, we aim to pave the way for MK-based diagnostics and therapies that could present promising tools in the diagnosis and treatment of cardiovascular diseases.

Functions of chondroitin/dermatan sulfate containing GalNAc4,6-disulfate

Chondroitin sulfate (CS) and dermatan sulfate (DS) containing GalNAc4,6-disulfate (GalNAc4S6S) were initially discovered in marine animals. Following the discovery, these glycosaminoglycans have been found in various animals including human. In the biosynthesis of CS/DS containing GalNAc4S6S, three groups of sulfotransferases are involved; chondroitin 4-sulfotransferases (C4STs), dermatan 4-sulfotransferase-1 (D4ST-1) and GalNAc 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST). GalNAc4S-6ST and its products have been shown to play important roles in the abnormal pathological conditions such as central nervous system injury, cancer development, abnormal tissue fibrosis, development of osteoporosis, and infection with viruses or nematodes. CS/DS containing GalNAc4S6S has been shown to increase with the functional differentiation of mast cells, macrophages and neutrophils. Genetic approaches using knockout or knockdown of GalNAc4S-6ST, blocking of the epitopes containing GalNAc4S6S by specific antibodies and chemical technology that enabled the synthesis of oligosaccharides with defined sulfation patterns have been applied successfully to these investigations. These studies contributed significantly to the basic understanding of the functional roles of CS/DS containing GalNAc4S6S in various abnormal conditions, and appear to provide promising clues to the development of possible measures to treat them.

Chondroitin sulfate E alleviates β-amyloid toxicity in transgenic Caenorhabditis elegans by inhibiting its aggregation

Chondroitin sulfate E (CS-E), which is characterized by oversulfated disaccharide units, has been shown to regulate neuronal adhesion, neurite outgrowth and exert neuroprotective effects. In view of these findings, here we investigated the anti-Alzheimer's disease (AD) activities of CSE by using transgenic Caenorhabditis elegans model of Alzheimer's disease. The behavioral experiments demonstrated that CSE at the concentration of 1 mg/ml significantly delayed the worm paralysis caused by Aβ aggregation as compared with control group. Western blot analysis revealed that the level of small oligomers in the transgenic C. elegans was significantly reduced upon treatment with CSE. The number of Aβ plaque deposits in transgenic worm was significantly decreased. In addition, CSE also protected the worms from oxidative stress and rescued chemotaxis dysfunction in transgenic strain CL2355. Taken together, these data suggested that CSE could protect against Aβ-induced toxicity in C. elegans. These results offer valuable evidence for the future use of CSE in the development of agents for the treatment of AD.

Characterization of chondroitin sulfate in stem cells derived from umbilical cord blood in rats

Chondroitin sulfate (CS) and its isomeric variant, dermatan sulfate (DS), are complex glycosaminoglycans (GAGs) which are ubiquitous components of the extracellular matrix in various tissues including the brain. CS and/or DS are known to bind to a variety of growth factors and regulate many cellular events such as proliferation and differentiation. Although the biological activities of CS and/or DS towards neural stem/progenitor cells (NSPCs) have been well investigated, the CS and/or DS of hematopoietic stem cells (HSCs) have not been fully characterized. Here, we analyzed GAGs on mononuclear cells of rat umbilical cord blood cells (UCB-MNCs). CS was detected in vascular intima and media of rat umbilical cord at embryonic day 19 (E19) by immunohistochemistry. The stem-cell-enriched-UCBCs (SCE-UCBCs), which were expanded from rat UCB-MNCs, expressed CS. CS chains are composed of repeating disaccharide units, which are classified into several types such as O-, A-, B-, C-, D-, and E-unit according to the number and positions of sulfation. A disaccharide composition analysis revealed that CS and/or DS were abundant in rat UCB-MNCs as well as in their expanded SCE-UCBCs, while the amount of heparan sulfate (HS) was less. The degree of sulfation of CS/DS was relatively low and the major component in UCB-MNCs and SCE-UCBCs was the A-unit. A colony-forming cell assay revealed that the percentage of colony-forming cells decreased in culture with CS degradation enzyme. The CS and/or DS of UCBCs may be involved in biological activities such as stem cell proliferation and/or differentiation.

A novel chondroitin sulfate E from Dosidicus gigas cartilage and its antitumor metastatic activity

Chondroitin sulfate (CS) chains containing GlcUAβ1-3GalNAc(4S,6S) (E unit) have been shown to be involved in various physiological and pathological processes. However, commercial E unit-rich CS (CS-E) is difficult to produce on a large scale due to expensive and limited squid cartilage resources. In this study, a novel CS-E (CS-nE) was isolated from the cheap and abundant cartilage of the giant squid Dosidicus gigas. The CS-nE has a surprisingly large molecular mass of 696 kDa and a relatively high E unit proportion (44.5 %). It can interact with various growth factors, including HGF, bFGF, pleiotrophin, and HB-EGF, with high affinity, and exhibits dose-dependent anti-metastatic activity. Furthermore, the E unit-rich decasaccharide selectively prepared from CS-nE has been shown to be the minimal functional domain with the strongest antitumor metastatic activity. Taken together, CS-nE will be a very promising candidate for the development of CS-E-based pharmaceutical products.

Research and Application of Chondroitin Sulfate/Dermatan Sulfate-Degrading Enzymes

Chondroitin sulfate (CS) and dermatan sulfate (DS) are widely distributed on the cell surface and in the extracellular matrix in the form of proteoglycan, where they participate in various biological processes. The diverse functions of CS/DS can be mainly attributed to their high structural variability. However, their structural complexity creates a big challenge for structural and functional studies of CS/DS. CS/DS-degrading enzymes with different specific activities are irreplaceable tools that could be used to solve this problem. Depending on the site of action, CS/DS-degrading enzymes can be classified as glycosidic bond-cleaving enzymes and sulfatases from animals and microorganisms. As discussed in this review, a few of the identified enzymes, particularly those from bacteria, have wildly applied to the basic studies and applications of CS/DS, such as disaccharide composition analysis, the preparation of bioactive oligosaccharides, oligosaccharide sequencing, and potential medical application, but these do not fulfill all of the needs in terms of the structural complexity of CS/DS.

Glycosaminoglycans in Neurodegenerative Diseases

Glycosaminoglycans (GAGs) are linear polysaccharides that consist of alternating disaccharides sequences of uronic acids and/or galactose hexamino sugars most of which are sulfated. GAGs are ubiquitously expressed on the cell surface, in the intracellular milieu and in the extracellular matrix of all animal cells. Thus, GAGs exhibit many essential roles in a variety of physiological and pathological processes. The targets of GAGs are GAG-binding proteins and related proteins that are of significant interest to both the academic community and in the pharmaceutical industry. In this review, the structures of GAGs, their binding proteins, and analogs are presented that further the development of GAGs and their analogs for the treatment of neurodegenerative diseases agents.

[Hereditary Skeletal and Skin Disorders Caused by Defects in the Biosynthesis of Chondroitin/Dermatan Sulfate, and Molecular Mechanisms of Pulmonary Metastasis]

The roles of chondroitin sulfate (CS) and dermatan sulfate (DS) have been demonstrated in various biological events such as the construction of the extracellular matrix, tissue development, and cell signaling through interactions with extracellular matrix components, morphogens, and growth factors. Human genetic diseases, including skeletal abnormalities, connective tissue diseases, and heart defects, were reported to be caused by mutations in the genes encoding glycosyltransferases, epimerases, and sulfotransferases that are responsible for the biosynthesis of CS and DS. Glycobiological approaches revealed that mutations in CS- and DS-biosynthetic enzymes led to reductions in their enzymatic activities and in the levels of CS and DS. Furthermore, CS at the surface of tumor cells plays a key role in pulmonary metastasis. A receptor for advanced glycation end-products (RAGE) was predominantly expressed in the lung, and was identified as a functional receptor for CS chains. CS and anti-RAGE antibodies inhibited the pulmonary metastasis of not only Lewis lung carcinoma but also B16 melanoma cells. Hence, RAGE and CS are potential targets of drug discovery for pulmonary metastasis and a number of other pathological conditions involving RAGE in the pathogenetic mechanism. This review provides an overview of glycobiological studies on characterized genetic disorders caused by the impaired biosynthesis of CS, as well as DS, and on the pulmonary metastasis of Lewis lung carcinoma cells involving CS and RAGE.

Glycosaminoglycan-based biomaterials for growth factor and cytokine delivery: Making the right choices

Controlled, localized drug delivery is a long-standing goal of medical research, realization of which could reduce the harmful side-effects of drugs and allow more effective treatment of wounds, cancers, organ damage and other diseases. This is particularly the case for protein "drugs" and other therapeutic biological cargoes, which can be challenging to deliver effectively by conventional systemic administration. However, developing biocompatible materials that can sequester large quantities of protein and release them in a sustained and controlled manner has proven challenging. Glycosaminoglycans (GAGs) represent a promising class of bio-derived materials that possess these key properties and can additionally potentially enhance the biological effects of the delivered protein. They are a diverse group of linear polysaccharides with varied functionalities and suitabilities for different cargoes. However, most investigations so far have focused on a relatively small subset of GAGs - particularly heparin, a readily available, promiscuously-binding GAG. There is emerging evidence that for many applications other GAGs are in fact more suitable for regulated and sustained delivery. In this review, we aim to illuminate the beneficial properties of various GAGs with reference to specific protein cargoes, and to provide guidelines for informed choice of GAGs for therapeutic applications.

Galactosaminoglycans: Medical Applications and Drawbacks

Galactosaminoglycans (GalAGs) are sulfated glycans composed of alternating N-acetylgalactosamine and uronic acid units. Uronic acid epimerization, sulfation patterns and fucosylation are modifications observed on these molecules. GalAGs have been extensively studied and exploited because of their multiple biomedical functions. Chondroitin sulfates (CSs), the main representative family of GalAGs, have been used in alternative therapy of joint pain/inflammation and osteoarthritis. The relatively novel fucosylated chondroitin sulfate (FCS), commonly found in sea cucumbers, has been screened in multiple systems in addition to its widely studied anticoagulant action. Biomedical properties of GalAGs are directly dependent on the sugar composition, presence or lack of fucose branches, as well as sulfation patterns. Although research interest in GalAGs has increased considerably over the three last decades, perhaps motivated by the parallel progress of glycomics, serious questions concerning the effectiveness and potential side effects of GalAGs have recently been raised. Doubts have centered particularly on the beneficial functions of CS-based therapeutic supplements and the potential harmful effects of FCS as similarly observed for oversulfated chondroitin sulfate, as a contaminant of heparin. Unexpected components were also detected in CS-based pharmaceutical preparations. This review therefore aims to offer a discussion on (1) the current and potential therapeutic applications of GalAGs, including those of unique features extracted from marine sources, and (2) the potential drawbacks of this class of molecules when applied to medicine.

The Role of Midkine in Arteriogenesis, Involving Mechanosensing, Endothelial Cell Proliferation, and Vasodilation

Mechanical forces in blood circulation such as shear stress play a predominant role in many physiological and pathophysiological processes related to vascular responses or vessel remodeling. Arteriogenesis, defined as the growth of pre-existing arterioles into functional collateral arteries compensating for stenosed or occluded arteries, is such a process. Midkine, a pleiotropic protein and growth factor, has originally been identified to orchestrate embryonic development. In the adult organism its expression is restricted to distinct tissues (including tumors), whereby midkine is strongly expressed in inflamed tissue and has been shown to promote inflammation. Recent investigations conferred midkine an important function in vascular remodeling and growth. In this review, we introduce the midkine gene and protein along with its cognate receptors, and highlight its role in inflammation and the vascular system with special emphasis on arteriogenesis, particularly focusing on shear stress-mediated vascular cell proliferation and vasodilatation.

Harnessing chondroitin sulphate in composite scaffolds to direct progenitor and stem cell function for tissue repair

This review details the inclusion of chondroitin sulphate in bioscaffolds for superior functional properties in tissue regenerative applications.

Chondroitin sulfates and their binding molecules in the central nervous system

Chondroitin sulfate (CS) is the most abundant glycosaminoglycan (GAG) in the central nervous system (CNS) matrix. Its sulfation and epimerization patterns give rise to different forms of CS, which enables it to interact specifically and with a significant affinity with various signalling molecules in the matrix including growth factors, receptors and guidance molecules. These interactions control numerous biological and pathological processes, during development and in adulthood. In this review, we describe the specific interactions of different families of proteins involved in various physiological and cognitive mechanisms with CSs in CNS matrix. A better understanding of these interactions could promote a development of inhibitors to treat neurodegenerative diseases.

Degree of Suppression of Mouse Myoblast Cell Line C₂C12 Differentiation Varies According to Chondroitin Sulfate Subtype

Chondroitin sulfate (CS), a type of glycosaminoglycan (GAG), is a factor involved in the suppression of myogenic differentiation. CS comprises two repeating sugars and has different subtypes depending on the position and number of bonded sulfate groups. However, the effect of each subtype on myogenic differentiation remains unclear. In this study, we spiked cultures of C₂C₁₂ myoblasts, cells which are capable of undergoing skeletal muscle differentiation, with one of five types of CS (CS-A, -B, -C, -D, or -E) and induced differentiation over a fixed time. After immunostaining of the formed myotubes with an anti-MHC antibody, we counted the number of nuclei in the myotubes and then calculated the fusion index (FI) as a measure of myotube differentiation. The FI values of all the CS-treated groups were lower than the FI value of the control group, especially the group treated with CS-E, which displayed notable suppression of myotube formation. To confirm that the sugar chain in CS-E is important in the suppression of differentiation, chondroitinase ABC (ChABC), which catabolizes CS, was added to the media. The addition of ChABC led to the degradation of CS-E, and neutralized the suppression of myotube formation by CS-E. Collectively, it can be concluded that the degree of suppression of differentiation depends on the subtype of CS and that CS-E strongly suppresses myogenic differentiation. We conclude that the CS sugar chain has inhibitory action against myoblast cell fusion.

Sugar-dependent modulation of neuronal development, regeneration, and plasticity by chondroitin sulfate proteoglycans

Chondroitin sulfate proteoglycans (CSPGs) play important roles in the developing and mature nervous system, where they guide axons, maintain stable connections, restrict synaptic plasticity, and prevent axon regeneration following CNS injury. The chondroitin sulfate glycosaminoglycan (CS GAG) chains that decorate CSPGs are essential for their functions. Through these sugar chains, CSPGs are able to bind and regulate the activity of a diverse range of proteins. CSPGs have been found both to promote and inhibit neuronal growth. They can promote neurite outgrowth by binding to various growth factors such as midkine (MK), pleiotrophin (PTN), brain-derived neurotrophic factor (BDNF) and other neurotrophin family members. CSPGs can also inhibit neuronal growth and limit plasticity by interacting with transmembrane receptors such as protein tyrosine phosphatase σ (PTPσ), leukocyte common antigen-related (LAR) receptor protein tyrosine phosphatase, and the Nogo receptors 1 and 3 (NgR1 and NgR3). These CS-protein interactions depend on specific sulfation patterns within the CS GAG chains, and accordingly, particular CS sulfation motifs are upregulated during development, in the mature nervous system, and in response to CNS injury. Thus, spatiotemporal regulation of CS GAG biosynthesis may provide an important mechanism to control the functions of CSPGs and to modulate intracellular signaling pathways. Here, we will discuss these sulfation-dependent processes and highlight how the CS sugars on CSPGs contribute to neuronal growth, axon guidance, and plasticity in the nervous system.

Sugar glues for broken neurons

Proteoglycans (PGs) regulate diverse functions in the central nervous system (CNS) by interacting with a number of growth factors, matrix proteins, and cell surface molecules. Heparan sulfate (HS) and chondroitin sulfate (CS) are two major glycosaminoglycans present in the PGs of the CNS. The functionality of these PGs is to a large extent dictated by the fine sulfation patterns present on their glycosaminoglycan (GAG) chains. In the past 15 years, there has been a significant expansion in our knowledge on the role of HS and CS chains in various neurological processes, such as neuronal growth, regeneration, plasticity, and pathfinding. However, defining the relation between distinct sulfation patterns of the GAGs and their functionality has thus far been difficult. With the emergence of novel tools for the synthesis of defined GAG structures, and techniques for their characterization, we are now in a better position to explore the structure-function relation of GAGs in the context of their sulfation patterns. In this review, we discuss the importance of GAGs on CNS development, injury, and disorders with an emphasis on their sulfation patterns. Finally, we outline several GAG-based therapeutic strategies to exploit GAG chains for ameliorating various CNS disorders.

Chondroitin Sulfate Induces Depression of Synaptic Transmission and Modulation of Neuronal Plasticity in Rat Hippocampal Slices

It is currently known that in CNS the extracellular matrix is involved in synaptic stabilization and limitation of synaptic plasticity. However, it has been reported that the treatment with chondroitinase following injury allows the formation of new synapses and increased plasticity and functional recovery. So, we hypothesize that some components of extracellular matrix may modulate synaptic transmission. To test this hypothesis we evaluated the effects of chondroitin sulphate (CS) on excitatory synaptic transmission, cellular excitability, and neuronal plasticity using extracellular recordings in the CA1 area of rat hippocampal slices. CS caused a reversible depression of evoked field excitatory postsynaptic potentials in a concentration-dependent manner. CS also reduced the population spike amplitude evoked after orthodromic stimulation but not when the population spikes were antidromically evoked; in this last case a potentiation was observed. CS also enhanced paired-pulse facilitation and long-term potentiation. Our study provides evidence that CS, a major component of the brain perineuronal net and extracellular matrix, has a function beyond the structural one, namely, the modulation of synaptic transmission and neuronal plasticity in the hippocampus.

Syntheses of chondroitin sulfate tetrasaccharide structures containing 4,6-disulfate patterns and analysis of their interaction with glycosaminoglycan-binding protein

Chondroitin sulfate tetrasaccharide ligand conjugates, namely GlcA-GalNAc6S-GlcA-GalNAc4S6S (CS-C+E) 1, GlcA2S-GalNAc6S-GlcA2S-GalNAc4S6S (CS-D+T) 2, GlcA-GalNAc4S6S-GlcA-GalNAc4S (CS-E+A) 3, GlcA-GalNAc4S6S-GlcA-GalNAc6S (CS-E+C) 4, and GlcA-GalNAc4S6S-GlcA-GalNAc4S6S (CS-E+E) 5, were systematically synthesized using a disaccharide building block 6. Synthesized CS tetrasaccharide structures were immobilized onto gold-coated chips to prepare array-type sugar chips, and the binding properties of protein were evaluated by surface plasmon resonance imaging biosensor. CS-D+T, CS-E+A, CS-E+C, and CS-E+E showed greater affinity for basic fibroblast growth factor than did other tetrasaccharides (CS-C+D, C+E, D+D).

Chondroitin 4-O-sulfotransferases are required for cell adhesion and morphogenesis in the Ciona intestinalis embryo

Chondroitin sulfate (CS) is a carbohydrate component of proteoglycans. Several types of sulfotransferases determine the pattern of CS sulfation, and thus regulate the biological functions of proteoglycans. The protochordate ascidians are the closest relatives of vertebrates, but the functions of their sulfotransferases have not been investigated. Here, we show that two chondroitin 4-O-sulfotransferases (C4STs) play important roles in the embryonic morphogenesis of the ascidian Ciona intestinalis. Ci-C4ST-like1 is predominantly expressed in the epidermis and muscle. Epidermal and muscle cells became spherical upon the injection of a Ci-C4ST-like1-specific morpholino oligo (MO), thus suggesting weakened cell adhesion. Co-injection of a Ci-C4ST-like1-expressing transgene rescued the phenotype, suggesting that the effects of the MO were specific. Ci-C4ST-like3 was expressed in the central nervous system, muscle, and mesenchyme. A specific MO appeared to affect cell adhesion in the epidermis and muscle. Convergent extension movement of notochordal cells was also impaired. Forced expression of Ci-C4ST-like3 restored normal morphogenesis, suggesting that the effects of the MO were specific. The present study suggests that Ci-C4ST-like1 and Ci-C4ST-like3 are required for cell adhesion mainly in the epidermis and muscle.

Chondroitin 6-O-sulfotransferases are required for morphogenesis of the notochord in the ascidian embryo

BACKGROUND

Chondroitin sulfate (CS) is a sulfated polysaccharide chain that binds to various core proteins to form proteoglycans. The amount and position of sulfate groups in CS are variable among different tissues, and are determined by specific sulfotransferases. Although the ascidians are the closest relatives of vertebrates, the functions of their sulfotransferases have not been studied.

RESULTS

The genome of the ascidian Ciona intestinalis contains eight genes encoding proteins similar to chondroitin 6-O-sulfotransferases (C6STs), which appear to have independently diverged in the ascidian lineage during evolution. Among them, Ci-C6ST-like1 and Ci-C6ST-like7 were predominantly expressed in the developing notochord. In addition, they were weakly expressed in the neural tube. The disruption of either one of them affected the convergent extension movement of notochordal cells. Presumptive notochord cells coming from both sides of the embryo did not intercalate. The results suggest that both of them are necessary. In some cases, the anterior neural tube failed to close. Forced expression of Ci-C6ST-like1 or Ci-C6ST-like7 in the notochord restored the normal intercalation of notochordal cells, indicating that the effects of morpholino oligos are specific.

CONCLUSIONS

Ci-C6ST-like1 and Ci-C6ST-like7 are required for the morphogenesis of the notochord in the ascidian embryo.

Stereocontrolled preparation of biotinylated chondroitin sulfate E di-, tetra-, and hexasaccharide conjugates

The synthesis of biotinylated conjugates of oligomers of the basic repeating unit of chondroitin sulfate E (CS-E) with the sequence [GlcA-4,6-disulfated GalNAc]n is reported herein for the first time. An efficient and stereocontrolled preparation of di-, tetra-, and hexasaccharide derivatives was achieved using a common key disaccharide intermediate in an iterative way. An unexpected and never reported side reaction on the carbonyl group of the levulinate ester was observed during a coupling reaction. These complex molecules should be useful to study their interactions with various proteins.

Sulfated glycosaminoglycans control the extracellular trafficking and the activity of the metalloprotease inhibitor TIMP-3

Tissue inhibitor of metalloproteinase 3 (TIMP-3) is an important regulator of extracellular matrix (ECM) turnover. TIMP-3 binds to sulfated ECM glycosaminoglycans or is endocytosed by cells via low-density lipoprotein receptor-related protein 1 (LRP-1). Here, we report that heparan sulfate (HS) and chondroitin sulfate E (CSE) selectively regulate postsecretory trafficking of TIMP-3 by inhibiting its binding to LRP-1. HS and CSE also increased TIMP-3 affinity for glycan-binding metalloproteinases, such as adamalysin-like metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), by reducing the dissociation rate constants. The sulfation pattern was crucial for these activities because monosulfated or truncated heparin had a reduced ability to bind to TIMP-3 and increase its affinity for ADAMTS-5. Therefore, sulfation of ECM glycans regulates the levels and inhibitory activity of TIMP-3 and modulates ECM turnover, and small mimicries of sulfated glycans may protect the tissue from the excess destruction seen in diseases such as osteoarthritis, cancer, and atherosclerosis.

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The metalloprotease inhibitor TIMP-3 binds to sulfated extracellular glycans

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This inhibits cellular uptake of TIMP-3 by the endocytic receptor LRP-1

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Glycans also increase TIMP-3 affinity for selected target proteases

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The sulfation of matrix glycans therefore modulates TIMP-3 activity and ECM turnover

Synthesis of Chondroitin Sulfate E Hexasaccharide in the Repeating Region by an Effective Elongation Strategy toward Longer Chondroitin Oligosaccharide

We synthesized chondroitin and its sulfate E hexasaccharides (1 and 2) composed of the trimer of the repeating disaccharide, beta-D-GalNAc(+/-4,6-di-O-SO(3)Na)-(1-->4)-beta-D-GlcA, by employing an efficient synthetic strategy for longer chondroitin oligosaccharide. Successful elongation with the beta-D-GalNAc-(1-->4)-beta-D-GlcA unit instead of the corresponding disaccharide possessing an azide group avoided problematic reduction of the multiple azide groups on the hexasaccharide.

Structure and function of midkine as the basis of its pharmacological effects

Midkine (MK) is a heparin-binding growth factor or cytokine and forms a small protein family, the other member of which is pleiotrophin. MK enhances survival, migration, cytokine expression, differentiation and other activities of target cells. MK is involved in various physiological processes, such as development, reproduction and repair, and also plays important roles in the pathogenesis of inflammatory and malignant diseases. MK is largely composed of two domains, namely a more N-terminally located N-domain and a more C-terminally located C-domain. Both domains are basically composed of three antiparallel β-sheets. In addition, there are short tails in the N-terminal and C-terminal sides and a hinge connecting the two domains. Several membrane proteins have been identified as MK receptors: receptor protein tyrosine phosphatase Z1 (PTPζ), low-density lipoprotein receptor-related protein, integrins, neuroglycan C, anaplastic lymphoma kinase and Notch-2. Among them, the most established one is PTPζ. It is a transmembrane tyrosine phophatase with chondroitin sulfate, which is essential for high-affinity binding with MK. PI3K and MAPK play important roles in the downstream signalling system of MK, while transcription factors affected by MK signalling include NF-κB, Hes-1 and STATs. Because of the involvement of MK in various physiological and pathological processes, MK itself as well as pharmaceuticals targeting MK and its signalling system are expected to be valuable for the treatment of numerous diseases.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

The cytokine midkine supports neutrophil trafficking during acute inflammation by promoting adhesion via β2 integrins (CD11/CD18)

Emerging evidence suggests a role of the cytokine midkine (MK) in inflammation. In this study, its functional relevance for recruitment of polymorphonuclear neutrophils (PMNs) during acute inflammation was investigated. Intravital microscopy and histologic analysis of tumor necrosis factor-α-stimulated cremaster muscle venules revealed severely compromised leukocyte adhesion and extravasation in MK(-/-) mice compared with MK(+/+) animals. Systemic administration of recombinant MK completely rescued the adhesion defect in MK(-/-) mice. In a hind limb ischemia model, leukocyte accumulation in MK(-/-) mice was significantly diminished compared with MK(+/+) animals. However, MK did not lead to an inflammatory activation of PMNs or endothelial cells suggesting that it does not serve as classical proinflammatory cytokine. Unexpectedly, immobilized MK mediated PMN adhesion under static and flow conditions, whereas PMN-derived MK was dispensable for the induction of adhesion. Furthermore, adhesion strengthening remained unaffected by MK. Flow cytometry revealed that immobilized, but not soluble MK, significantly promoted the high affinity conformation of β2 integrins of PMNs. Blocking studies of low-density lipoprotein receptor-related protein 1 (LRP1) suggested that LRP1 may act as a receptor for MK on PMNs. Thus, MK seems to support PMN adhesion by promoting the high affinity conformation of β2 integrins, thereby facilitating PMN trafficking during acute inflammation.

Exploiting differential surface display of chondroitin sulfate variants for directing neuronal outgrowth

Chondroitin sulfate (CS) proteoglycans (CSPGs) are known to be primary inhibitors of neuronal regeneration at scar sites. However, a variety of CSPGs are also involved in neuronal growth and guidance during other physiological stages. Sulfation patterns of CS chains influence their interactions with various growth factors in the central nervous system (CNS), thus influencing neuronal growth, inhibition, and pathfinding. This report demonstrates the use of differentially sulfated CS chains for neuronal navigation. Surface-immobilized patterns of CS glycosaminoglycan chains were used to determine neuronal preference toward specific sulfations of five CS variants: CS-A, CS-B (dermatan sulfate), CS-C, CS-D, and CS-E. Neurons preferred CS-A, CS-B, and CS-E and avoided CS-C containing lanes. In addition, significant alignment of neurites was observed using underlying lanes containing CS-A, CS-B, and CS-E chains. To utilize differential preference of neurons toward the CS variants, a binary combinations of CS chains were created by backfilling a neuro-preferred CS variant between the microcontact printed lanes of CS-C stripes, which are avoided by neurons. The neuronal outgrowth results demonstrate for the first time that a combination of sulfation variants of CS chains without any protein component of CSPG is sufficient for directing neuronal outgrowth. Biomaterials with surface immobilized GAG chains could find numerous applications as bridging devices for tackling CNS injuries where directional growth of neurons is critical for recovery.

Construction of a chondroitin sulfate library with defined structures and analysis of molecular interactions

Chondroitin sulfate (CS) is a linear acidic polysaccharide, composed of repeating disaccharide units of glucuronic acid and N-acetyl-D-galactosamine and modified with sulfate residues at different positions, which plays various roles in development and disease. Here, we chemo-enzymatically synthesized various CS species with defined lengths and defined sulfate compositions, from chondroitin hexasaccharide conjugated with hexamethylenediamine at the reducing ends, using bacterial chondroitin polymerase and recombinant CS sulfotransferases, including chondroitin-4-sulfotransferase 1 (C4ST-1), chondroitin-6-sulfotransferase 1 (C6ST-1), N-acetylgalactosamine 4-sulfate 6-sulfotransferase (GalNAc4S-6ST), and uronosyl 2-sulfotransferase (UA2ST). Sequential modifications of CS with a series of CS sulfotransferases revealed their distinct features, including their substrate specificities. Reactions with chondroitin polymerase generated non-sulfated chondroitin, and those with C4ST-1 and C6ST-1 generated uniformly sulfated CS containing >95% 4S and 6S units, respectively. GalNAc4S-6ST and UA2ST generated highly sulfated CS possessing ∼90% corresponding disulfated disaccharide units. Sequential reactions with UA2ST and GalNAc4S-6ST generated further highly sulfated CS containing a mixed structure of disulfated units. Surprisingly, sequential reactions with GalNAc4S-6ST and UA2ST generated a novel CS molecule containing ∼29% trisulfated disaccharide units. Enzyme-linked immunosorbent assay and surface plasmon resonance analysis using the CS library and natural CS products modified with biotin at the reducing ends, revealed details of the interactions of CS species with anti-CS antibodies, and with CS-binding molecules such as midkine and pleiotrophin. Chemo-enzymatic synthesis enables the generation of CS chains of the desired lengths, compositions, and distinct structures, and the resulting library will be a useful tool for studies of CS functions.

A highly-sulfated chondroitin sulfate, CS-E, adsorbs specifically to neurons with nuclear condensation

A highly sulfated chondroitin sulfate, CS-E, prevents excitatory amino acid-induced neuronal cell death by an as yet unknown mechanism. To reveal this mechanism, we pretreated neurons in culture with various inhibitors, and examined whether N-methyl-D-aspartic acid (NMDA)-induced neuronal cell death was reduced in the presence of CS-E. The inhibitors of protein kinase C (PKC) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) ameliorated NMDA-induced neuronal cell death, but did not affect the neuroprotective activity of CS-E. Among the growth factors with which CS-E can interact, high concentration of BDNF protected against the NMDA-induced neuronal cell death and strengthened neuroprotection by CS-E. CS-E, but neither CS-A nor CS-C, adsorbed to a subclass of neurons with nuclear condensation, namely pyknosis. Contactin-1 (CNTN-1), a putative receptor for neuritogenic activity of CS-E, was present in cortical neurons, but a neutralizing antibody to CNTN-1 did not block neuroprotective activity of CS-E. The results suggest that CS-E may prevent the progression of cell death at the early stages of excitotoxicity through a signaling pathway different from CNTN-1.

Astrocytes as a source for extracellular matrix molecules and cytokines

Research of the past 25 years has shown that astrocytes do more than participating and building up the blood-brain barrier and detoxify the active synapse by reuptake of neurotransmitters and ions. Indeed, astrocytes express neurotransmitter receptors and, as a consequence, respond to stimuli. Within the tripartite synapse, the astrocytes owe more and more importance. Besides the functional aspects the differentiation of astrocytes has gained a more intensive focus. Deeper knowledge of the differentiation processes during development of the central nervous system might help explaining and even help treating neurological diseases like Alzheimer’s disease, Amyotrophic lateral sclerosis, Parkinsons disease, and psychiatric disorders in which astrocytes have been shown to play a role. Specific differentiation of neural stem cells toward the astroglial lineage is performed as a multi-step process. Astrocytes and oligodendrocytes develop from a multipotent stem cell that prior to this has produced primarily neuronal precursor cells. This switch toward the more astroglial differentiation is regulated by a change in receptor composition on the cell surface and responsiveness to Fibroblast growth factor and Epidermal growth factor (EGF). The glial precursor cell is driven into the astroglial direction by signaling molecules like Ciliary neurotrophic factor, Bone Morphogenetic Proteins, and EGF. However, the early astrocytes influence their environment not only by releasing and responding to diverse soluble factors but also express a wide range of extracellular matrix (ECM) molecules, in particular proteoglycans of the lectican family and tenascins. Lately these ECM molecules have been shown to participate in glial development. In this regard, especially the matrix protein Tenascin C (Tnc) proved to be an important regulator of astrocyte precursor cell proliferation and migration during spinal cord development. Nevertheless, ECM molecules expressed by reactive astrocytes are also known to act mostly in an inhibitory fashion under pathophysiological conditions. Thus, we further summarize resent data concerning the role of chondroitin sulfate proteoglycans and Tnc under pathological conditions.

Midkine in the pathology of cancer, neural disease, and inflammation

Midkine (MK) is a heparin-binding growth factor involved in various cellular processes such as cellular proliferation, survival, and migration. In addition to these typical growth factor activities, MK exhibits several other activities related to fibrinolysis, blood pressure, host defense and other processes. Many cell-surface receptors have been identified to account for the multiple biological activities of MK. The expression of MK is frequently upregulated in many types of human carcinoma. Moreover, blood MK levels are closely correlated with patient outcome. Knockdown and blockade of MK suppress tumorigenesis and tumor development. Thus, MK serves as a tumor marker and a molecular target for cancer therapy. Furthermore, there is growing evidence that MK plays pivotal roles in neural and inflammatory diseases. Understanding of the mechanisms of action of MK is expected to create new therapeutic options for several human diseases.

Semi-synthesis of chondroitin sulfate-E from chondroitin sulfate-A

Chondroitin sulfate-E (chondroitin-4, 6-disulfate) was prepared from chondroitin sulfate-A (chondroitin-4 - sulfate) by regioselective sulfonation, performed using trimethylamine sulfur trioxide in formamide under argon. The structure of semi-synthetic chondroitin sulfate-E was analyzed by PAGE, (1)H NMR, (13)C NMR, 2D NMR and disaccharide analysis and compared with natural chondroitin sulfate-E. Both semi-synthetic and natural chondroitin sulfate-E were each biotinylated and immobilized on BIAcore SA biochips and their interactions with fibroblast growth factors displayed very similar binding kinetics and binding affinities. The current semi-synthesis offers an economical approach for the preparation of the rare chondroitin sulfate-E from the readily available chondroitin sulfate-A.

Nutraceutical functionalities of polysaccharides from marine invertebrates

Many researchers are seeking functional materials from marine resources. These marine resources can be used as traditional food additives, and specifically, these are based on polysaccharides. To date, there is a big opportunity to develop new high-value added products with indispensable functional characteristics, which can be used in nutraceuticals either as additives or supplements. Also, a crossover in the pharmaceutical market may be established. Some glycosaminoglycans (GAGs) mimetic-type molecules are already being utilized in the field of nutrition as well as in the cosmetics industry. This chemical is used as a dietary supplement to maintain the structure and function of cartilages, for the relief of pain caused by osteoarthritic joints, and can also be used as an anti-inflammatory agent. Recently, in relation to the prevalence of mad cow disease and avian influenza, the production of GAGs from marine invertebrates offers new market opportunities as compared with that obtained from bovine or avian livestock.

Midkine in inflammation

The 13 kDa heparin-binding growth factor midkine (MK) was originally identified as a molecule involved in the orchestration of embryonic development. Recent studies provided evidence for a new role of MK in acute and chronic inflammatory processes. Accordingly, several inflammatory diseases including nephritis, arthritis, atherosclerosis, colitis, and autoimmune encephalitis have been shown to be alleviated in the absence of MK in animal models. Reduced leukocyte recruitment to the sites of inflammation was found to be one important mechanism attenuating chronic inflammation when MK was absent. Furthermore, MK was found to modulate expression of proinflammatory cytokines and the expansion of regulatory T-cells. Here, we review the current understanding of the role of MK in different inflammatory disorders and summarize the knowledge of MK biology.

Characterization of chondroitin sulfate from deer tip antler and osteogenic properties

Deer antler is a highly regenerative tissue that involves cellular differentiation, osteogenesis and ossification processes. Chondroitin sulfate is the major glycosaminoglycan contained in antler connective tissue and has been isolated from cartilaginous antler by 4 M GuHCl extraction, gradient ultracentrifugation and chromatography techniques. We examined the disaccharide composition by 2-AB labeling and anion exchange HPLC analysis of the three resultant fractions (high, medium and low density fractions). The high density fraction consists of A-unit and D-unit disaccharide in the ratio of 1:1, whereas, the CS disaccharide composition ratio of A- unit:C-unit:D-Unit:E-unit contained in medium and low density fractions are 3:4:3:1 and 2:2:2:1, respectively. The only intact CS oligosaccharides of the medium density fraction upregulated gene expression of bone-specific proteins of a human osteoblastic cell line (hFOB1.19). Thus, CS oligosaccharides from cartilaginous deer antler, with their oversulfated chondroitin sulfate composition, demonstrated the physiological properties and may be good candidates for osteogenetic agents in humans.

Dermatan sulfate in tunicate phylogeny: order-specific sulfation pattern and the effect of [→4IdoA(2-sulfate)β-1→3GalNAc(4-sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity

Background

Previously, we have reported the presence of highly sulfated dermatans in solitary ascidians from the orders Phlebobranchia (Phallusia nigra) and Stolidobranchia (Halocynthia pyriformis and Styela plicata). Despite the identical disaccharide backbone, consisting of [→4IdoA(2S)β-1→3GalNAcβ-1→], those polymers differ in the position of sulfation on the N-Acetyl galactosamine, which can occur at carbon 4 or 6. We have shown that position rather than degree of sulfation is important for heparin cofactor II activity. As a consequence, 2,4- and 2,6-sulfated dermatans have high and low heparin cofactor II activities, respectively. In the present study we extended the disaccharide analysis of ascidian dermatan sulfates to additional species of the orders Stolidobranchia (Herdmania pallida, Halocynthia roretzi) and Phlebobranchia (Ciona intestinalis), aiming to investigate how sulfation evolved within Tunicata. In addition, we analysed how heparin cofactor II activity responds to dermatan sulfates containing different proportions of 2,6- or 2,4-disulfated units.

Results

Disaccharide analyses indicated a high content of disulfated disaccharide units in the dermatan sulfates from both orders. However, the degree of sulfation decreased from Stolidobranchia to Phlebobranchia. While 76% of the disaccharide units in dermatan sulfates from stolidobranch ascidians are disulfated, 53% of disulfated disaccharides are found in dermatan sulfates from phlebobranch ascidians. Besides this notable difference in the sulfation degree, dermatan sulfates from phlebobranch ascidians contain mainly 2,6-sulfated disaccharides whereas dermatan sulfate from the stolidobranch ascidians contain mostly 2,4-sulfated disaccharides, suggesting that the biosynthesis of dermatan sulfates might be differently regulated during tunicates evolution. Changes in the position of sulfation on N-acetylgalactosamine in the disaccharide [→4IdoA(2-Sulfate)β-1→3GalNAcβ-1→] modulate heparin cofactor II activity of dermatan sulfate polymers. Thus, high and low heparin cofactor II stimulating activity is observed in 2,4-sulfated dermatan sulfates and 2,6-sulfated dermatan sulfates, respectively, confirming the clear correlation between the anticoagulant activities of dermatan sulfates and the presence of 2,4-sulfated units.

Conclusions

Our results indicate that in ascidian dermatan sulfates the position of sulfation on the GalNAc in the disaccharide [→4IdoA(2S)β-1→3GalNAcβ-1→] is directly related to the taxon and that the 6-O sulfation is a novelty apparently restricted to the Phlebobranchia. We also show that the increased content of [→4IdoA(2S)β-1→3GalNAc(4S)β-1→] disaccharide units in dermatan sulfates from Stolidobranchia accounts for the increased heparin cofactor II stimulating activity.

Midkine as a factor to counteract the deposition of amyloid β-peptide plaques: in vitro analysis and examination in knockout mice

Background

Midkine is a heparin-binding cytokine involved in cell survival and various inflammatory processes. Midkine accumulates in senile plaques of patients with Alzheimer's disease, while it counteracts the cytotoxic effects of amyloid β-peptide and inhibits its oligomerization. The present study was conducted to understand the role of midkine upon plaque formation of amyloid β-peptide.

Methods

A surface plasmon assay was performed to determine the affinity of midkine for amyloid β-peptide. The deposition of amyloid β-peptide was compared in the brain of wild-type and midkine-deficient mice. An effect of midkine to microglias was examined by cell migration assay.

Results

Midkine bound to amyloid β-peptide with the affinity of 160 nM. The C-terminal half bound to the peptide more strongly than the N-terminal half, and heparin inhibited midkine from binding to the peptide. Pleiotrophin, which has about 50% sequence identity with midkine also bound to amyloid β-peptide. The deposition of amyloid β-peptide plaques in the cortex and hippocampus was more intense in 15-month-old midkine-deficient mice, compared to the corresponding wild-type mice. Midkine promoted migration of microglias in culture.

Conclusions

These results are consistent with the view that midkine attenuates the deposition of amyloid β-peptide plaques, and thus progression of Alzheimer's disease, by direct binding and also by promoting migration of microglias.