Lysine 58 and histidine 66 at the C-terminal alpha-helix of monocyte chemoattractant protein-1 are essential for glycosaminoglycan binding

Heparin, an active excipient to carry biosignal molecules: Applications in tissue engineering - A review

Drug repositioning refers to new medical application exploration for existing drugs. Heparins, beyond their well-known anticoagulant properties widely used in clinics, present the capacity to carry biosignal molecules that is responsible for other properties such as anti-inflammatory, angiogenesis. Thus, heparins interaction with different biosignal molecules such as cytokines and growth factors have recently drawn attention and have promoted heparin repositioning as an active excipient with useful applications as drug-delivery systems and biomaterial-based tissue engineering scaffolds. Indeed, biomaterial heparinization can further help in their formulation such as in self-assembled heparin-based hydrogels or nanoparticles, and improve their biocompatibility. Moreover, the capacity of heparin to carry biosignal molecules enables the direct functionalization of heparinized biomaterial for tissue engineering. Both heparin characteristics namely the biosignal molecule carrying and biomaterial heparinization are reviewed here along their combination for biomaterial functionalization in tissue engineering applications.

Female and male obese Zucker rats display differential inflammatory mediator and long non-coding RNA profiles

AIMS

The goal of this study was to identify mediators in peri-lymphatic adipose tissue (PLAT) that are altered in obese versus lean Zucker rats, with focus on potential sex differences MAIN METHODS: Mesenteric PLAT was analyzed with protein and lncRNA arrays. Additional RT-PCR confirmation was performed with epididymal/ovarian fat.

KEY FINDINGS

MCP-1, TCK-1, Galectin-1, Galectin-3, and neuropilin-1 were elevated in PLAT from obese rats of both sexes. However, 11 additional proteins were elevated only in obese males while 24 different proteins were elevated in obese females. Profiling of lncRNAs revealed lean males have elevated levels of NEAT1, MALAT1 and GAS5 compared to lean females. NEAT1, MALAT1, and GAS5 were significantly reduced with obesity in males but not in females. Another lncRNA, HOTAIR, was higher in lean females compared to males, and its levels in females were reduced with obesity. Obese rats of both sexes had similar histologic findings of mesenteric macrophage crown-like structures and hepatocyte fat accumulation.

SIGNIFICANCE

While obese male and female Zucker rats both have increased inflammation, they have distinct signals. Future studies of the proteome and lncRNA landscape of obese males vs. females in various animal models and in human subjects are warranted to better guide development of therapeutics for obesity-induced inflammation.

Characterization of canine adipose- and endometrium-derived Mesenchymal Stem/Stromal Cells and response to lipopolysaccharide

Mesenchymal stem/stromal cells (MSCs) are used for regenerative therapy in companion animals. Their potential was initially attributed to multipotency, but subsequent studies in rodents, humans and veterinary species evidenced that MSCs produce factors that are key mediators of immune, anti-infective and angiogenic responses, which are essential in tissue repair. MSCs preparations have been classically obtained from bone marrow and adipose tissue (AT) in live animals, what requires the use of surgical procedures. In contrast, the uterus, which is naturally exposed to external insult and infection, can be accessed nonsurgically to obtain samples, or tissues can be taken after neutering. In this study, we explored the endometrium (EM) as an alternative source of MSCs, which we compared with AT obtained from canine paired samples. Canine AT- and EM-MSCs, formed CFUs when seeded at low density, underwent tri-lineage differentiation into adipocytes, osteocytes and chondrocytes, and expressed the CD markers CD73, CD90 and CD105, at equivalent levels. The immune genes IL8, CCL2 and CCL5 were equally expressed at basal levels by both cell types. However, in the presence of the inflammatory stimulus lipopolysaccharide (LPS), expression of IL8 was higher in EM- than in AT-MSCs (p < 0.04) while the other genes were equally elevated in both cell types (p < 0.03). This contrasted with the results for CD markers, where the expression was unaltered by exposing the MSCs to LPS. Overall, the results indicate that canine EM-MSCs could serve as an alternative cell source to AT-MSCs in therapeutic applications.

Heparin Specifically Interacts with Basic BBXB Motifs of the Chemokine CCL21 to Define CCR7 Signaling

Chemokines are critically involved in controlling directed leukocyte migration. Spatiotemporal secretion together with local retention processes establish and maintain local chemokine gradients that guide directional cell migration. Extracellular matrix proteins, particularly glycosaminoglycans (GAGs), locally retain chemokines through electrochemical interactions. The two chemokines CCL19 and CCL21 guide CCR7-expressing leukocytes, such as antigen-bearing dendritic cells and T lymphocytes, to draining lymph nodes to initiate adaptive immune responses. CCL21-in contrast to CCL19-is characterized by a unique extended C-terminus composed of highly charged residues to facilitate interactions with GAGs. Notably, both chemokines can trigger common, but also ligand-biased signaling through the same receptor. The underlying molecular mechanism of ligand-biased CCR7 signaling is poorly understood. Using a series of naturally occurring chemokine variants in combination with newly designed site-specific chemokine mutants, we herein assessed CCR7 signaling, as well as GAG interactions. We demonstrate that the charged chemokine C-terminus does not fully confer CCL21-biased CCR7 signaling. Besides the positively charged C-terminus, CCL21 also possesses specific BBXB motifs comprising basic amino acids. We show that CCL21 variants where individual BBXB motifs are mutated retain their capability to trigger G-protein-dependent CCR7 signaling, but lose their ability to interact with heparin. Moreover, we show that heparin specifically interacts with CCL21, but not with CCL19, and thereby competes with ligand-binding to CCR7 and prevents signaling. Hence, we provide evidence that soluble heparin, but not the other GAGs, complexes with CCL21 to define CCR7 signaling in a ligand-dependent manner.

The Role of Heparan Sulfate in CCL26-Induced Eosinophil Chemotaxis

Proinflammatory chemokine ligand 26 (CCL26, eotaxin-3) mediates transendothelial cell migration of eosinophils by binding and activating the G-protein-coupled (GPC) chemokine receptor 3 on the surface of eosinophilic cells. Here we have investigated the role of glycosaminoglycans (GAGs) as potential co-receptors in the process of CCL26-induced eosinophil chemotaxis. For this purpose, we have first identified the GAG-binding site of CCL26 by a site-directed mutagenesis approach in the form of an alanine screening. A panel of GAG-binding-deficient mutants has been designed, generated, and analyzed with respect to their binding affinities to heparan sulphate (HS) by isothermal fluorescence titration studies. This showed that basic amino acids in the α-helical part of CCL26 are strongly involved in GAG-binding. In chemotaxis experiments, we found that decreased GAG-binding affinity correlated with decreased chemotactic activity, which indicates an involvement of GAGs in eosinophil migration. This was further proven by the negative impact of heparinase III treatment and, independently, by the incubation of eosinophils with an anti heparan sulfate antibody. We finally investigated eosinophils’ proteoglycan (PG) expression patterns by real-time PCR, which revealed the highest expression level for serglycin. Including an anti-serglycin antibody in CCL26-induced eosinophil migration experiments reduced the chemotaxis of these immune cells, thereby proving the dependence of eosinophil mobilization on the proteoglycan serglycin.

Fat Grafts Augmented With Vitamin E Improve Volume Retention and Radiation-Induced Fibrosis

BACKGROUND

Treatments for radiation-induced fibrosis range from vitamin E and pentoxifylline systemically to deferoxamine and fat grafting locally. Regarding fat grafting, volume retention hinders its long-term functionality and is affected by two factors: inflammation and necrosis secondary to hypovascularity.

OBJECTIVE

We aimed to simultaneously improve fat graft retention and radiation-induced fibrosis by integrating vitamin E and pentoxifylline into fat grafts locally.

METHODS

Forty adult CD-1 nude male mice at 6 weeks of age underwent scalp irradiation and recovered for four weeks to allow for the development of fibrosis. Mice received 200μL of donor human fat graft to the scalp. Mice were separated into 4 conditions: no grafting, fat graft without treatment, graft treated with pentoxifylline, and graft treated with vitamin E. Fat graft volume retention was monitored in-vivo using microCT scans at weeks 0, 1, 2, 4, 6, and 8 after grafting. Histological and cytokine analysis of the scalp skin and fat grafts were also performed.

RESULTS

Vitamin E (VE) treated grafts had significant improvement in dermal thickness and collagen density of overlying skin compared to all other groups. VE decreased 8-isoprostane and increased CD31 + staining compared to the other grafted groups. Cytokine analysis revealed decreased inflammatory and increased angiogenic markers in both the fat graft and overlying skin of the vitamin E group. Fat graft volume retention was significantly improved in the vitamin E group starting at 1 week post grafting.

CONCLUSION

Radiation-induced fibrosis and fat graft volume retention are both simultaneously improved with local administration of vitamin E.

Heparanase is a regulator of natural killer cell activation and cytotoxicity

Heparanase is the only mammalian enzyme capable of cleaving heparan sulfate, a glycosaminoglycan of the extracellular matrix and cell surfaces. Most immune cells express heparanase that contributes to a range of functions including cell migration and cytokine expression. Heparanase also promotes natural killer (NK) cell migration; however, its role in other NK cell functions remains to be defined. In this study, heparanase-deficient (Hpse^-/- ) mice were used to assess the role of heparanase in NK cell cytotoxicity, activation, and cytokine production. Upon challenge with the immunostimulant polyinosinic:polycytidylic acid (poly(I:C)), NK cells isolated from Hpse^-/- mice displayed impaired cytotoxicity against EO771.LMB cells and reduced levels of activation markers CD69 and NKG2D. However, in vitro cytokine stimulation of wild-type and Hpse^-/- NK cells resulted in similar CD69 and NKG2D expression, suggesting the impaired NK cell activation in Hpse^-/- mice results from elements within the in vivo niche. NK cells are activated in vivo by dendritic cells (DCs) in response to poly(I:C). Poly(I:C)-stimulated Hpse^-/- bone marrow DCs (BMDCs) expressed less IL-12, and when cultured with Hpse^-/- NK cells, less MCP-1 mRNA and protein was detected. Although cell-cell contact is important for DC-mediated NK cell activation, co-cultures of Hpse^-/- BMDCs and NK cells showed similar levels of contact to wild-type cells, suggesting heparanase contributes to NK cell activation independently of cell-cell contact with DCs. These observations define a role for heparanase in NK cell cytotoxicity and activation and have important implications for how heparanase inhibitors currently in clinical trials for metastatic cancer may impact NK cell immunosurveillance.

The Heparanase Regulatory Network in Health and Disease

The extracellular matrix (ECM) is a structural framework that has many important physiological functions which include maintaining tissue structure and integrity, serving as a barrier to invading pathogens, and acting as a reservoir for bioactive molecules. This cellular scaffold is made up of various types of macromolecules including heparan sulfate proteoglycans (HSPGs). HSPGs comprise a protein core linked to the complex glycosaminoglycan heparan sulfate (HS), the remodeling of which is important for many physiological processes such as wound healing as well as pathological processes including cancer metastasis. Turnover of HS is tightly regulated by a single enzyme capable of cleaving HS side chains: heparanase. Heparanase upregulation has been identified in many inflammatory diseases including atherosclerosis, fibrosis, and cancer, where it has been shown to play multiple roles in processes such as epithelial-mesenchymal transition, angiogenesis, and cancer metastasis. Heparanase expression and activity are tightly regulated. Understanding the regulation of heparanase and its downstream targets is attractive for the development of treatments for these diseases. This review provides a comprehensive overview of the regulators of heparanase as well as the enzyme's downstream gene and protein targets, and implications for the development of new therapeutic strategies.

Establishment and characterization of a new human first trimester Trophoblast cell line, AL07

INTRODUCTION

The limited cell number of primary trophoblasts and contamination of trophoblast cell lines promote us to develop a novel stable trophoblast cell line.

METHOD OF STUDY

Primary trophoblast cells were isolated from first-trimester placenta and telomerase-induced immortalization was used to immortalize these cells. Subsets of cells were then evaluated by flow cytometry using CK7, HLA-G, CD45 and CD14, specific markers for trophoblast cells, extra-villous trophoblast, pan leucocyte and monocyte/macrophage, respectively. Immunofluorescence staining and immunocytochemistry were used to detect CK7 expression in trophoblast cells. The level of secreted human Chorionic Gonadotropin (hCG) was measured by electrochemiluminescence (ECL). The Bio-Plex MAGPIX System was used to analyze the cytokines and chemokines produced by AL07 cell line.

RESULTS

We were able to isolate primary trophoblast cells from several first-trimester placentas. One clone, AL07 trophoblast cells, isolated from a week 7 placenta, was morphologically stable and positive for the expression of CK7 by immunofluorescence and immunocytochemistry staining. Characterization of AL07 cells reveled that they are CD45 or CD14 negative and had constitutive secretion of hCG and low HLA-G expression. Furthermore, clone AL07 secret high levels of several cytokines and chemokines, including IL-6, IL-8 and VEGF, and moderately secreted MCP-1 IP-10 and RANTES.

DISCUSSION

We report the successful isolation, immortalization and characterization of AL07 cells, a novel cell clone isolated from first trimester human placenta. The clone is free of contamination of immune cells, and exhibits similar cytokine profile as other trophoblast cell lines. This new cytotrophoblast-like AL07 cell, can be a valuable tool for in-vitro trophoblast studies in the future.

Targeting Chemokine-Glycosaminoglycan Interactions to Inhibit Inflammation

Leukocyte migration into tissues depends on the activity of chemokines that form concentration gradients to guide leukocytes to a specific site. Interaction of chemokines with their specific G protein-coupled receptors (GPCRs) on leukocytes induces leukocyte adhesion to the endothelial cells, followed by extravasation of the leukocytes and subsequent directed migration along the chemotactic gradient. Interaction of chemokines with glycosaminoglycans (GAGs) is crucial for extravasation in vivo. Chemokines need to interact with GAGs on endothelial cells and in the extracellular matrix in tissues in order to be presented on the endothelium of blood vessels and to create a concentration gradient. Local chemokine retention establishes a chemokine gradient and prevents diffusion and degradation. During the last two decades, research aiming at reducing chemokine activity mainly focused on the identification of inhibitors of the interaction between chemokines and their cognate GPCRs. This approach only resulted in limited success. However, an alternative strategy, targeting chemokine-GAG interactions, may be a promising approach to inhibit chemokine activity and inflammation. On this line, proteins derived from viruses and parasites that bind chemokines or GAGs may have the potential to interfere with chemokine-GAG interactions. Alternatively, chemokine mimetics, including truncated chemokines and mutant chemokines, can compete with chemokines for binding to GAGs. Such truncated or mutated chemokines are characterized by a strong binding affinity for GAGs and abrogated binding to their chemokine receptors. Finally, Spiegelmers that mask the GAG-binding site on chemokines, thereby preventing chemokine-GAG interactions, were developed. In this review, the importance of GAGs for chemokine activity in vivo and strategies that could be employed to target chemokine-GAG interactions will be discussed in the context of inflammation.

Surface plasmon resonance imaging coupled to on-chip mass spectrometry: a new tool to probe protein-GAG interactions

A biosensor device for the detection and characterization of protein-glycosaminoglycan interactions is being actively sought and constitutes the key to identifying specific carbohydrate ligands, an important issue in glycoscience. Mass spectrometry (MS) hyphenated methods are promising approaches for carbohydrate enrichment and subsequent structural characterization. In the study herein, we report the analysis of interactions between the glycosaminoglycans (GAGs) heparin (HP) and heparan sulfate (HS) and various cytokines by coupling surface plasmon resonance imaging (SPRi) for thermodynamic analysis method and MALDI-TOF MS for structural determination. To do so, we developed an SPR biochip in a microarray format and functionalized it with a self-assembled monolayer of short poly(ethylene oxide) chains for grafting the human cytokines stromal cell-derived factor-1 (SDF-1α), monocyte chemotactic protein-1 (MCP-1), and interferon-γ. The thermodynamic parameters of the interactions between these cytokines and unfractionated HP/HS and derived oligosaccharides were successively determined using SPRi monitoring, and the identification of the captured carbohydrates was carried out directly on the biochip surface using MALDI-TOF MS, revealing cytokine preferential affinity for GAGs. The MS identification was enhanced by on-chip digestion of the cytokine-bound GAGs with heparinase, leading to the detection of oligosaccharides likely involved in the binding sequence of GAG ligands. Although several carbohydrate array-based assays have been reported, this study is the first report of the successful analysis of protein-GAG interactions using SPRi-MS coupling.

Factors Associated with RANTES Concentration in Cardiovascular Disease Patients

Objective

The aim of the study was to establish, by means of linear regressions analysis, whether RANTES and CCL2 have a relationship with age, sex, heart rate, ejection fraction, white blood cells count, monocyte count, platelet count, mean platelet volume, hsCRP concentration, creatinine and eGFR value, applied treatments, and coronary risk factors in polish cardiovascular disease patients.

Methods

Plasma chemokines concentrations were measured by ELISA method (R&D Systems Europe Ltd., Abingdon, England) in 115 cardiovascular disease patients (83 myocardial infarction/AMI and 32 stable angina/SA) and in the control group (N=25).

Results

Univariate linear regression analysis found that (1) for men mean RANTES plasma level is 1.56 times higher as compared to women; (2) if patient's age increases by 1 year, the mean RANTES concentration value increases by 1.4%; (3) if CCL2 concentration increases by 10 pg/mL, the mean RANTES concentration value increases by 3.3%; (4) if hsCRP concentration increases by 1 mg/L, the mean RANTES concentration value increases by 1.0%. By means of multiple linear regression analysis we found that (1) for men the mean plasma RANTES concentration value increases 1.89 times as compared to women; (2) if CCL2 concentration increases by 10 pg/mL, the mean RANTES concentration value increases by 3.4%; (3) if MPV increases by 1 fL, the mean RANTES concentration value increases by 12%, if other model parameters are fixed. For CCL2 we did not obtain statistically significant linear regression models.

Conclusion

Due to high variability of obtained CCL2 concentrations, it seems that RANTES better reflects the presence of the atherosclerotic lesion than CCL2. RANTES as a marker of atherosclerotic process may be an important therapeutic target, and the assessment of RANTES concentration should be interpreted depending on patient's sex, age, platelet hyperactivity state, hsCRP, and CCL2 concentration.

A mini review on immune role of chemokines and its receptors in snakehead murrel Channa striatus

Chemokines are ubiquitous cytokine molecules involved in migration of cells during inflammation and normal physiological processes. Though the study on chemokines in mammalian species like humans have been extensively studied, characterization of chemokines in teleost fishes is still in the early stage. The present review provides an overview of chemokines and its receptors in a teleost fish, Channa striatus. C. striatus is an air breathing freshwater carnivore, which has enormous economic importance. This species is affected by an oomycete fungus, Aphanomyces invadans and a Gram negative bacteria Aeromonas hydrophila is known to cause secondary infection. These pathogens impose immune changes in the host organism, which in turn mounts several immune responses. Of these, the role of cytokines in the immune response is immense, due to their involvement in several activities of inflammation such as cell trafficking to the site of inflammation and antigen presentation. Given that importance, chemokines in fishes do have significant role in the immunological and other physiological functions of the organism, hence there is a need to understand the characteristics, activities and performace of these small molecules in details.

Glycosaminoglycan-based hydrogels capture inflammatory chemokines and rescue defective wound healing in mice

Excessive production of inflammatory chemokines can cause chronic inflammation and thus impair cutaneous wound healing. Capturing chemokine signals using wound dressing materials may offer powerful new treatment modalities for chronic wounds. Here, a modular hydrogel based on end-functionalized star-shaped polyethylene glycol (starPEG) and derivatives of the glycosaminoglycan (GAG) heparin was customized for maximal chemokine sequestration. The material is shown to effectively scavenge the inflammatory chemokines MCP-1 (monocyte chemoattractant protein-1), IL-8 (interleukin-8), and MIP-1α (macrophage inflammatory protein-1α) and MIP-1β (macrophage inflammatory protein-1β) in wound fluids from patients suffering from chronic venous leg ulcers and to reduce the migratory activity of human monocytes and polymorphonuclear neutrophils. In an in vivo model of delayed wound healing (db/db mice), starPEG-GAG hydrogels outperformed the standard-of-care product Promogran with respect to reduction of inflammation, as well as increased granulation tissue formation, vascularization, and wound closure.

Monitoring Scavenging Activity of Chemokine Receptors

Migration and positioning of cells is fundamental for complex functioning of multicellular organisms. During an immune response, cells are recruited from remote distances to a distinct location. Cells that are passively transported leave the circulation stimulated by locally produced signals and follow chemotactic cues to reach specific destinations. Such gradients are short (<150 μm) and require a source of production where the concentration is the highest and a sink in apposition where the attractant dissipates and the concentration is the lowest. Several straight forward methods exist to identify in vitro and in vivo cells producing chemoattractants. This can be achieved at the transcriptional level and by measuring secreted proteins. However, to demonstrate the activity of sinks in vitro and in vivo is more challenging. Cell-mediated dissipation of an attractant must be revealed by measuring its uptake and subsequent destruction. Elimination of chemoattractants such as chemokines can be monitored in vitro using radiolabeled ligands or more elegantly with fluorescent-labeled chemoattractants. The latter method can also be used in vivo and enables to monitor the process in real time using time-lapse video microscopy. In this chapter, we describe methods to produce fluorescently labeled chemokines either as fusion proteins secreted from insect cells or as recombinant bacterial proteins that can enzymatically be labeled. We discuss methods that were successfully used to demonstrate sink activities of scavenger receptors. Moreover, fluorescent chemokines can be used to noninvasively analyze receptor expression and activity in living cells.

Breast cancer: coordinated regulation of CCL2 secretion by intracellular glycosaminoglycans and chemokine motifs

The chemokine CCL2 (MCP-1) has been identified as a prominent tumor-promoting factor in breast cancer. The major source for CCL2 is in the tumor cells; thus, identifying the mechanisms regulating CCL2 release by these cells may enable the future design of modalities inhibiting CCL2 secretion and consequently reduce tumorigenicity. Using cells deficient in expression of glycosaminoglycans (GAGs) and short hairpin RNAs reducing heparan sulfate (HS) and chondroitin sulfate (CS) expression, we found that intracellular HS and CS (= GAGs) partly controlled the trafficking of CCL2 from the Golgi toward secretion. Next, we determined the secretion levels of GFP-CCL2-WT and GFP-CCL2-variants mutated in GAG-binding domains and/or in the 40s loop of CCL2 (⁴⁵TIVA⁴⁸). We have identified partial roles for R18+K19, H66, and the ⁴⁵TIVA⁴⁸ motif in regulating CCL2 secretion. We have also demonstrated that in the absence of R24 or R18+K19 +⁴⁵TIVA⁴⁸, the secretion of CCL2 by breast tumor cells was almost abolished. Analyses of the intracellular localization of GFP-CCL2-mutants in the Golgi or the endoplasmic reticulum revealed particular intracellular processes in which these CCL2 sequences controlled its intracellular trafficking and secretion. The R24, ⁴⁵TIVA⁴⁸ and R18+K19 +⁴⁵TIVA⁴⁸ domains controlled CCL2 secretion also in other cell types. We propose that targeting these chemokine regions may lead to reduced secretion of CCL2 by breast cancer cells (and potentially also by other malignant cells). Such a modality may limit tumor growth and metastasis, presumably without affecting general immune activities (as discussed below).

Crystal structure of a mirror-image L-RNA aptamer (Spiegelmer) in complex with the natural L-protein target CCL2

We report the crystal structure of a 40mer mirror-image RNA oligonucleotide completely built from nucleotides of the non-natural L-chirality in complex with the pro-inflammatory chemokine L-CLL2 (monocyte chemoattractant protein-1), a natural protein composed of regular L-amino acids. The L-oligonucleotide is an L-aptamer (a Spiegelmer) identified to bind L-CCL2 with high affinity, thereby neutralizing the chemokine's activity. CCL2 plays a key role in attracting and positioning monocytes; its overexpression in several inflammatory diseases makes CCL2 an interesting pharmacological target. The PEGylated form of the L-aptamer, NOX-E36 (emapticap pegol), already showed promising efficacy in clinical Phase II studies conducted in diabetic nephropathy patients. The structure of the L-oligonucleotide·L-protein complex was solved and refined to 2.05 Å. It unveils the L-aptamer's intramolecular contacts and permits a detailed analysis of its structure–function relationship. Furthermore, the analysis of the intermolecular drug–target interactions reveals insight into the selectivity of the L-aptamer for certain related chemokines.

Spiegelmers are ‘mirror image' L-ribose oligonucleotides being developed as therapeutics. Here the authors present a crystal structure of the therapeutic L-aptamer NOX-E36 bound to the pro-inflammatory chemokine CLL2, providing insight into NOX-E36's selectivity and mode of action.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Demystifying heparan sulfate-protein interactions

Numerous proteins, including cytokines and chemokines, enzymes and enzyme inhibitors, extracellular matrix proteins, and membrane receptors, bind heparin. Although they are traditionally classified as heparin-binding proteins, under normal physiological conditions these proteins actually interact with the heparan sulfate chains of one or more membrane or extracellular proteoglycans. Thus, they are more appropriately classified as heparan sulfate-binding proteins (HSBPs). This review provides an overview of the various modes of interaction between heparan sulfate and HSBPs, emphasizing biochemical and structural insights that improve our understanding of the many biological functions of heparan sulfate.

A beginner's guide to chemokines

This review provides an overview of chemokines and their receptors, with an emphasis on general features and nomenclature along with a short summary of their properties and functions. It is intended as an introduction to the subject and a reference point for those wishing to learn key facts about chemokines and their role in biology.

The CCL2 synthesis inhibitor bindarit targets cells of the neurovascular unit, and suppresses experimental autoimmune encephalomyelitis

BACKGROUND

Production of the chemokine CCL2 by cells of the neurovascular unit (NVU) drives critical aspects of neuroinflammation. Suppression of CCL2 therefore holds promise in treating neuroinflammatory disease. Accordingly, we sought to determine if the compound bindarit, which inhibits CCL2 synthesis, could repress the three NVU sources of CCL2 most commonly reported in neuroinflammation--astrocytes, microglia and brain microvascular endothelial cells (BMEC)--as well as modify the clinical course of neuroinflammatory disease.

METHODS

The effect of bindarit on CCL2 expression by cultured murine astrocytes, microglia and BMEC was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bindarit action on mouse brain and spinal cord in vivo was similarly investigated by qRT-PCR following LPS injection in mice. And to further gauge the potential remedial effects of bindarit on neuroinflammatory disease, its impact on the clinical course of experimental autoimmune encephalomyelitis (EAE) in mice was also explored.

RESULTS

Bindarit repressed CCL2 expression by all three cultured cells, and antagonized upregulated expression of CCL2 in both brain and spinal cord in vivo following LPS administration. Bindarit also significantly modified the course and severity of clinical EAE, diminished the incidence and onset of disease, and evidenced signs of disease reversal.

CONCLUSION

Bindarit was effective in suppressing CCL2 expression by cultured NVU cells as well as brain and spinal cord tissue in vivo. It further modulated the course of clinical EAE in both preventative and therapeutic ways. Collectively, these results suggest that bindarit might prove an effective treatment for neuroinflammatory disease.

Synthetic peptide fragment (65-76) of monocyte chemotactic protein-1 (MCP-1) inhibits MCP-1 binding to heparin and possesses anti-inflammatory activity in stable angina patients after coronary stenting

OBJECTIVE AND DESIGN

The peptide from C-terminal domain of MCP-1 (Ingramon) has been shown to inhibit monocyte migration and possess anti-inflammatory activity in animal models of inflammation and post-angioplasty restenosis. Here, we investigate the effect of Ingramon treatment on blood levels of acute-phase reactants and chemokines in patients after coronary stenting and the mechanisms of Ingramon anti-inflammatory activity.

SUBJECTS

Eighty-seven patients with ischemic heart disease (IHD) who faced the necessity of coronary angiography (CA) were enrolled. In 67 patients, one-stage coronary stenting was performed; 33 of them were treated with Ingramon in addition to standard therapy. Twenty patients underwent CA only.

METHODS

High-sensitivity C-reactive protein (hsCRP) and fibrinogen blood levels were detected routinely. The chemokine concentration in plasma was measured by enzyme-linked immunosorbent assay (ELISA) or cytometric bead array-based immunoassay. Intracellular Ca(2+) levels and cell surface integrin exposure were assayed by flow cytometry. MCP-1 dimerization was studied by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). MCP-1-heparin binding was assessed with a biosensor and ELISA.

RESULTS AND CONCLUSIONS

Ingramon treatment was accompanied by less pronounced elevation of hsCRP and fibrinogen levels and decreased MCP-1 concentration in plasma in patients after coronary stenting. Ingramon had no effect on MCP-1 interaction with cell receptors or MCP-1 dimerization, but inhibited MCP-1 binding to heparin. The anti-inflammatory activity of the peptide may be mediated by an impaired chemokine interaction with glycosaminoglycans.

Inhibition of antithrombin by Plasmodium falciparum histidine-rich protein II

Histidine-rich protein II (HRPII) is an abundant protein released into the bloodstream by Plasmodium falciparum, the parasite that causes the most severe form of human malaria. Here, we report that HRPII binds tightly and selectively to coagulation-active glycosaminoglycans (dermatan sulfate, heparan sulfate, and heparin) and inhibits antithrombin (AT). In purified systems, recombinant HRPII neutralized the heparin-catalyzed inhibition of factor Xa and thrombin by AT in a Zn(2+)-dependent manner. The observed 50% inhibitory concentration (IC(50)) for the HRPII neutralization of AT activity is approximately 30nM for factor Xa inhibition and 90nM for thrombin inhibition. Zn(2+) was required for these reactions with a distribution coefficient (K(d)) of approximately 7μM. Substituting Zn(2+) with Cu(2+), but not with Ca(2+), Mg(2+), or Fe(2+), maintained the HRPII effect. HRPII attenuated the prolongation in plasma clotting time induced by heparin, suggesting that HRPII inhibits AT activity by preventing its stimulation by heparin. In the microvasculature, where erythrocytes infected with P falciparum are sequestered, high levels of released HRPII may bind cellular glycosaminoglycans, prevent their interaction with AT, and thereby contribute to the procoagulant state associated with P falciparum infection.

MCP-1: chemoattractant with a role beyond immunity: a review

BACKGROUND

Monocyte Chemoattractant Protein (MCP)-1, a potent monocyte attractant, is a member of the CC chemokine subfamily. MCP-1 exerts its effects through binding to G-protein-coupled receptors on the surface of leukocytes targeted for activation and migration. Role of MCP-1 and its receptor CCR2 in monocyte recruitment during infection or under other inflammatory conditions is well known.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the role of MCP-1 in various allergic conditions, immunodeficiency diseases, bone remodelling, and permeability of blood - brain barrier, atherosclerosis, nephropathies and tumors.

CONCLUSION

MCP-1 plays an important role in pathogenesis of various disease states and hence MCP-1 inhibition may have beneficial effects in such conditions.

Monocyte chemoattractant protein-1 (MCP-1)/CCL2 secreted by hepatic myofibroblasts promotes migration and invasion of human hepatoma cells

The aim of our study was to investigate whether myofibroblasts and the chemokine monocyte chemoattractant protein-1 (MCP-1)/CCL2 may play a role in hepatocellular carcinoma progression. We observed that hepatic myofibroblast LI90 cells express MCP-1/CCL2 mRNA and secrete this chemokine. Moreover, myofibroblast LI90 cell-conditioned medium (LI90-CM) induces human hepatoma Huh7 cell migration and invasion. These effects are strongly reduced when a MCP-1/CCL2-depleted LI90-CM was used. We showed that MCP-1/CCL2 induces Huh7 cell migration and invasion through its G-protein-coupled receptor CCR2 and, to a lesser extent, through CCR1 only at high MCP-1/CCL2 concentrations. MCP-1/CCL2's chemotactic activities rely on tyrosine phosphorylation of focal adhesion components and depend on matrix metalloproteinase (MMP)-2 and MMP-9. Furthermore, we observed that Huh7 cell migration and invasion induced by the chemokine are strongly inhibited by heparin, by beta-D-xyloside treatment of cells and by anti-syndecan-1 and -4 antibodies. Finally, we developed a 3-dimensional coculture model of myofibroblast LI90 and Huh7 cells and demonstrated that MCP-1/CCL2 and its membrane partners, CCR1 and CCR2, may be involved in the formation of mixed hepatoma-myofibroblast spheroids. In conclusion, our data show that human liver myofibroblasts act on hepatoma cells in a paracrine manner to increase their invasiveness and suggest that myofibroblast-derived MCP-1/CCL2 could be involved in the pathogenesis of hepatocellular carcinoma.

Affinity-based microdialysis sampling using heparin for in vitro collection of human cytokines

Microdialysis sampling is a widely used method to sample from complex biological matrices. Cytokines are important signaling proteins that are typically recovered with low relative recovery values during microdialysis sampling. Heparin was included in the microdialysis perfusion fluid as an affinity agent to increase in vitro recovery of different cytokines through polyethersulfone (PES) microdialysis membranes with 100 kDa molecular weight cutoff. No change in fluid volumes collected from the microdialysis probes occurred when heparin was included in the perfusion fluid up to concentrations of 10 microM. The loss of heparin (10 microM) across the dialysis membrane was minimal (2.7+/-0.9%, n=3). Additionally, heparin at these concentrations did not interfere with the cytokine immunoassays. The control and heparin-enhanced relative recoveries for five human cytokines using 0.1 microM heparin in the microdialysis perfusion fluid flowing at 0.5 microL min(-1) were (n=3): interleukin-4 (IL-4), 4.2+/-0.5% and 7.2+/-3.1%; interleukin-6 (IL-6), 1.4+/-0.8% and 3.6+/-1.3%; interleukin-7 (IL-7), 1.3+/-0.8% and 4.8+/-1.8%; monocyte chemoattractant protein-1 (MCP-1), 9.0+/-1.6% and 19.5+/-2.7%; and tumor necrosis factor-alpha (TNF-alpha), 7.4+/-1.3% and 16.9+/-1.6%, respectively. Heparin increased the microdialysis sampling relative recovery of several human cytokines in vitro.

Sulfated oligosaccharides (heparin and fucoidan) binding and dimerization of stromal cell-derived factor-1 (SDF-1/CXCL 12) are coupled as evidenced by affinity CE-MS analysis

Chemokine stromal cell-derived factor-1 (SDF-1) is a potent chemoattractant involved in leukocyte trafficking and metastasis. Heparan sulfate on the cell surface binds SDF-1 and may modulate its function as a coreceptor of this chemokine. A major effect of the glycosaminoglycan binding may be on the quaternary structure of SDF-1, which has been controversially reported as a monomer or a dimer. We have investigated the effect of sulfated oligosaccharides on the oligomerization of SDF-1 and of its mutated form SDF-1 (3/6), using affinity capillary electrophoresis (ACE) hyphenated to mass spectrometry (MS). Coupled to MS, ACE allowed the study for the first time of the effect of size-defined oligosaccharides on the quaternary organization of SDF-1 in muM range concentrations, i.e., lower values than the mM values previously reported in NMR, light scattering, and ultracentrifugation experiments. Our results showed that in the absence of sulfated oligosaccharides, SDF-1 is mostly monomeric in solution. However, dimer formation was observed upon interaction with heparin-sulfated oligosaccharides despite the mM Kd values for dimerization. A SDF-1/oligosaccharide 2/1 complex was detected, indicating that oligosaccharide binding promoted the dimerization of SDF-1. Heparin tetrasaccharide but not disaccharide promoted dimer formation, suggesting that the dimer required to be stabilized by a long enough bound oligosaccharide. The SDF-1/oligosaccharide 1/1 complex was only observed with heparin disaccharide and fucoidan pentasaccharide, pointing out the role of specific structural determinants in promoting dimer formation. These results underline the importance of dimerization induced by glycosaminoglycans for chemokine functionality.

Monocyte-mediated defense against microbial pathogens

Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2-mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion, monocyte differentiation and trafficking, and finally monocyte-mediated microbial killing remain active and important areas of investigation.

Dual GPCR and GAG mimicry by the M3 chemokine decoy receptor

Viruses have evolved a myriad of evasion strategies focused on undermining chemokine-mediated immune surveillance, exemplified by the mouse γ-herpesvirus 68 M3 decoy receptor. Crystal structures of M3 in complex with C chemokine ligand 1/lymphotactin and CC chemokine ligand 2/monocyte chemoattractant protein 1 reveal that invariant chemokine features associated with G protein–coupled receptor binding are primarily recognized by the decoy C-terminal domain, whereas the N-terminal domain (NTD) reconfigures to engage divergent basic residue clusters on the surface of chemokines. Favorable electrostatic forces dramatically enhance the association kinetics of chemokine binding by M3, with a primary role ascribed to acidic NTD regions that effectively mimic glycosaminoglycan interactions. Thus, M3 employs two distinct mechanisms of chemical imitation to potently sequester chemokines, thereby inhibiting chemokine receptor binding events as well as the formation of chemotactic gradients necessary for directed leukocyte trafficking.

Perlecan: a major IL-2-binding proteoglycan in murine spleen

Although interleukin-2 (IL-2) is typically considered a soluble cytokine, our laboratory has shown that the availability of IL-2 in lymphoid tissues is regulated, in part, by an association with heparan sulfate glycosaminoglycan. Heparan sulfate is usually found in proteoglycan form, in which the heparan sulfate chains are covalently linked to a specific core protein. We now show that perlecan is one of the major IL-2-binding heparan sulfate proteoglycans in murine spleen. IL-2 binds perlecan via heparan sulfate chains, as enzymatic removal of heparan sulfate from splenic perlecan abolishes its ability to bind IL-2. Furthermore, we demonstrate that perlecan-bound IL-2 supports the proliferation of an IL-2-dependent cell line. Identification of perlecan as a major heparan sulfate proteoglycan that binds IL-2 has implications for both the localization and regulation of IL-2 in vivo.

Two C-terminal peptides of human CKLF1 interact with the chemokine receptor CCR4

Human chemokine-like factor 1 (CKLF1) exhibits chemotactic effects on leukocytes. A previous study demonstrated that CKLF1 is a functional ligand for human CC chemokine receptor 4 (CCR4). In this study, N-terminal amino acid sequencing of secreted CKLF1 protein showed that it contains at least two peptides, C27 and C19. To examine whether C27 or C19 play a role via CCR4, C27 and C19 were chemically synthesized and analyzed by chemotaxis, calcium mobilization, and receptor internalization assays in CCR4-tranfected HEK293 cells or Hut78 cells. The chemotaxis assay showed that C27 could induce chemotaxis to CCR4-transfected HEK293 cells or Hut78 cells while C19 had weaker chemotactic activity, especially in Hut78 cells. C27- or C19-induced chemotaxis was abolished by pertussis toxin, suggesting the involvement of a Gi/o pathway. C27- or C19-induced chemotaxis was also inhibited by an antagonist of CCR4 that show good binding potency, excellent chemotaxis inhibitory activity and selectivity toward CCR4, suggesting that their chemotactic activity specifically involved CCR4. The chemotactic response of CCR4-tranfected HEK293 cells to C27 or C19 was markedly inhibited by preincubation with TARC/CCL17. TARC/CCL17 effectively desensitized the calcium mobilization induced by C27 or C19. Similarly, both of C27 or C19 also desensitized the calcium mobilization and chemotaxis of CCR4-tranfected HEK293 cells in response to TARC/CCL17, suggesting that they might interact with a common receptor. Both C27- and C19-induced clear internalization of CCR4-EGFP. These results confirm that the secreted peptides of CKLF1, C27 and C19, have functional activation via CCR4.

Adiponectin binds to chemokines via the globular head and modulates interactions between chemokines and heparan sulfates

OBJECTIVE

Adiponectin, a fat cell-derived protein, has been attracting considerable attention because of its antidiabetic and antiatherogenic activities. The aim of the present study is to identify molecules physiologically associating with adiponectin and to understand how the protein displays diverse biological activities.

MATERIALS AND METHODS

We used an expression cloning method combined with enzyme-linked immunosorbent assay to clone adiponectin-binding proteins from the MS-5 complementary DNA library.

RESULTS

We successfully isolated two chemokines, stromal cell-derived factor-1 (SDF-1) and CCF18, and verified that adiponectin bound to them via its globular head. Adiponectin bound with various chemokines in vitro, such as macrophage-inflammatory protein-1alpha (MIP-1alpha), RANTES, and monocyte chemoattractant protein-1 (MCP-1), suggesting that the protein had a feature commonly to bind to the chemokine family. The middle part of chemokines, dispensable for interacting with their receptors, was found to be important for the adiponectin binding. Although the interaction of adiponectin to SDF-1 affected neither the SDF-1-CXCR4 binding nor the SDF-1 signaling in Jurkat cells, adiponectin and heparin mutually interfered in their association to SDF-1 and MCP-1 in vitro, implying that their association might influence the distribution of adiponectin and SDF-1 in inflammatory sites. Indeed, both adiponectin and SDF-1 was positively immunostained in vascular walls in guts from acute graft-vs-host disease patients. In addition, peripheral blood of adiponectin-deficient mice contained more hematopoietic progenitors than that of wild-type mice.

CONCLUSION

Adiponectin may be involved in regulation of inflammation via binding to specific chemokines. Additionally, the interaction possibly enables adiponectin to gather and play its role in inflammatory sites.

Throwing light on DARC

Chemokines play a key role in directing and driving leucocyte trafficking. The efficient regulation of leucocyte recruitment by chemokines requires their appropriate localization in functional micro-anatomical domains, as well as setting limits to their effects in space and time. Both processes are influenced by silent chemokine receptors (interceptors), including DARC (Duffy antigen receptor for chemokines). Increasing experimental evidence suggests that DARC is involved in accumulation of extravascular chemokines in endothelial cells, chemokine transcytosis and presentation on their luminal surface, leading to leucocyte adhesion and emigration. Additionally, DARC is expressed on erythrocytes and can act as a sink for chemokines in blood. This limits the dissemination of chemokines through blood into distant organs and tissues as well as reducing their effects on the circulating leucocytes.

The binding of CCL2 to the surface of Trypanosoma cruzi induces chemo-attraction and morphogenesis

Adhesion of Trypanosoma cruzi to host cells employs mechanisms which are complex and not completely understood. Upon infection, host cells release pro-inflammatory cytokines and chemokines in the environment. These had been found to be involved with increasing parasite uptake as well as killing by macrophages and cardiomyocytes. In the present study, we focused on the interaction of murine beta-chemokine CCL2 with trypomastigote forms of T. cruzi. We found that this chemokine directly triggers the chemotaxis and morphogenesis of trypomastigote forms of parasites. Binding assays showed that the interaction of CCL2 with molecules present in trypomastigote forms is abolished by the addition of condroitin 6-sulphate, a glycosaminoglycan. Moreover, we also observed that the parasite glycoproteins are the major players in this interaction. In summary, our study demonstrates a host ligand/parasite receptor interaction that may have relevant implications in the tissue tropism of this important parasitic disease.

CCL5-CCR5-mediated apoptosis in T cells: Requirement for glycosaminoglycan binding and CCL5 aggregation

CCL5 (RANTES (regulated on activation normal T cell expressed and secreted)) and its cognate receptor, CCR5, have been implicated in T cell activation. CCL5 binding to glycosaminoglycans (GAGs) on the cell surface or in extracellular matrix sequesters CCL5, thereby immobilizing CCL5 to provide the directional signal. In two CCR5-expressing human T cell lines, PM1.CCR5 and MOLT4.CCR5, and in human peripheral blood-derived T cells, micromolar concentrations of CCL5 induce apoptosis. CCL5-induced cell death involves the cytosolic release of cytochrome c, the activation of caspase-9 and caspase-3, and poly(ADP-ribose) polymerase cleavage. CCL5-induced apoptosis is CCR5-dependent, since native PM1 and MOLT4 cells lacking CCR5 expression are resistant to CCL5-induced cell death. Furthermore, we implicate tyrosine 339 as a critical residue involved in CCL5-induced apoptosis, since PM1 cells expressing a tyrosine mutant receptor, CCR5Y339F, do not undergo apoptosis. We show that CCL5-CCR5-mediated apoptosis is dependent on cell surface GAG binding. The addition of exogenous heparin and chondroitin sulfate and GAG digestion from the cell surface protect cells from apoptosis. Moreover, the non-GAG binding variant, (44AANA47)-CCL5, fails to induce apoptosis. To address the role of aggregation in CCL5-mediated apoptosis, nonaggregating CCL5 mutant E66S, which forms dimers, and E26A, which form tetramers at micromolar concentrations, were utilized. Unlike native CCL5, the E66S mutant fails to induce apoptosis, suggesting that tetramers are the minimal higher ordered CCL5 aggregates required for CCL5-induced apoptosis. Viewed altogether, these data suggest that CCL5-GAG binding and CCL5 aggregation are important for CCL5 activity in T cells, specifically in the context of CCR5-mediated apoptosis.

The biological relevance of chemokine–proteoglycan interactions

Chemokines exert their biological activity through high-affinity interactions with cell-surface receptors, thereby activating specific signalling pathways, and a second low-affinity interaction with proteoglycans. Proteoglycans consist of a protein core, to which GAG (glycosaminoglycan) chains are attached. The GAGs are long, linear, sulphated and highly charged heterogeneous polysaccharides that are expressed throughout the body in different forms depending on the developmental or pathological state of the organ/organism. Mechanistically, the GAG interaction is thought to facilitate the retention of chemokines on cell surfaces, thereby forming a high local concentration required for cell activation. Recently, we demonstrated that certain chemokines require interactions with GAGs for their in vivo function. Additionally we have shown that chemokines oligomerize on immobilized GAGs, and this ability to form higher order oligomers has also been shown to be essential for the activity of certain chemokines in vivo. We believe that interference with the chemokine–GAG interaction provides a novel anti-inflammatory strategy, exemplified by a variant of RANTES (regulated upon activation, normal T-cell expressed and secreted) that has abrogated GAG binding and oligomerization properties.

Structure activity relationships of monocyte chemoattractant proteins in complex with a blocking antibody

Monocyte chemoattractant proteins (MCPs) are cytokines that direct immune cells bearing appropriate receptors to sites of inflammation or injury and are therefore attractive therapeutic targets for inhibitory molecules. 11K2 is a blocking mouse monoclonal antibody active against several human and murine MCPs. A 2.5 A structure of the Fab fragment of this antibody in complex with human MCP-1 has been solved. The Fab blocks CCR2 receptor binding to MCP-1 through an adjacent but distinct binding site. The orientation of the Fab indicates that a single MCP-1 dimer will bind two 11K2 antibodies. Several key residues on the antibody and on human MCPs were predicted to be involved in antibody selectivity. Mutational analysis of these residues confirms their involvement in the antibody-chemokine interaction. In addition to mutations that decreased or disrupted binding, one antibody mutation resulted in a 70-fold increase in affinity for human MCP-2. A key residue missing in human MCP-3, a chemokine not recognized by the antibody, was identified and engineering the preferred residue into the chemokine conferred binding to the antibody.

Monocyte chemoattractant protein 1 released from glycosaminoglycans mediates its profibrotic effects in systemic sclerosis via the release of interleukin-4 from T cells

OBJECTIVE

Monocyte chemoattractant protein 1 (MCP-1; CCL2) has been implicated in the pathogenesis of fibrotic diseases and is up-regulated in patients with systemic sclerosis (SSc). The aim of the present study was to examine the mechanisms by which MCP-1 mediates its profibrotic effects in the setting of SSc.

METHODS

The expression of receptors for MCP-1 on dermal fibroblasts was analyzed by real-time polymerase chain reaction and fluorescence-activated cell sorting. The ability of extracellular matrix proteins to bind and release MCP-1 was quantified by enzyme-linked immunosorbent assay. Th0 cells were isolated using a magnetic-activated cell sorting system and were stimulated twice in the presence of MCP-1. The synthesis of collagen was measured using the Sircol collagen assay kit.

RESULTS

The glycosaminoglycan chondroitin sulfate, but not fibronectin or collagens, bound and released MCP-1 in a time-dependent manner. MCP-1 that was released from chondroitin sulfate induced the differentiation of interleukin-4 (IL-4)-producing T cells in a dose-dependent manner. In turn, dermal fibroblasts from patients with SSc expressed IL-4 receptor, and stimulation with IL-4 significantly increased the production of collagen in dermal fibroblasts. In contrast, CCR2a and CCR2b, as well as D6 and US28 (other potential receptors of MCP-1), were not detectable in SSc and normal fibroblasts, and their expression was not induced by platelet-derived growth factor, IL-1beta, or IL-4. In addition, MCP-1 had no direct effects on collagen production by fibroblasts.

CONCLUSION

MCP-1 has no direct effects on dermal fibroblasts but contributes to fibrosis in patients with SSc by inducing the differentiation of IL-4-producing T cells. Because MCP-1 has both proinflammatory and profibrotic effects, pharmacologic targeting of MCP-1 could be a promising therapeutic approach in SSc.

Blocking of monocyte chemoattractant protein-1 during tubulointerstitial nephritis resulted in delayed neutrophil clearance

The chemokine monocyte chemoattractant protein (MCP)-1 has been implicated in the monocyte/macrophage infiltration that occurs during tubulointerstitial nephritis (TIN). We investigated the role of MCP-1 in rats with TIN by administering a neutralizing anti-MCP-1 antibody (Ab). We observed significantly reduced macrophage infiltration and delayed neutrophil clearance in the kidneys of TIN model rats treated with the anti-MCP-1 Ab. To exclude the possibility that an observed immune complex could affect the resolution of apoptotic neutrophils via the Fc receptor, TIN model rats were treated with a peptide-based MCP-1 receptor antagonist (RA). The MCP-1 RA had effects similar to those of the anti-MCP-1 Ab. In addition, MCP-1 did not affect macrophage-mediated phagocytosis of neutrophils in vitro. Deposition of the anti-MCP-1 Ab in rat kidneys resulted from its binding to heparan sulfate-immobilized MCP-1, as demonstrated by the detection of MCP-1 in both pull-down and immunoprecipitation assays. We conclude that induction of chemokines, specifically MCP-1, in TIN corresponds with leukocyte infiltration and that the anti-MCP-1 Ab formed an immune complex with heparan sulfate-immobilized MCP-1 in the kidney. Antagonism of MCP-1 in TIN by Ab or RA may alter the pathological process, most likely through delayed removal of apoptotic neutrophils in the inflammatory loci.

Regulation of protein function by glycosaminoglycans--as exemplified by chemokines

Immune modulators such as cytokines and growth factors exert their biological activity through high-affinity interactions with cell-surface receptors, thereby activating specific signaling pathways. However, many of these molecules also participate in low-affinity interactions with another class of molecules, referred to as proteoglycans. Proteoglycans consist of a protein core to which glycosaminoglycan (GAG) chains are attached. The GAGs are long, linear, sulfated, and highly charged heterogeneous polysaccharides that are expressed throughout the body in different forms, depending on the developmental or pathological state of the organ/organism. They participate in many biological functions, including organogenesis and growth control, cell adhesion, signaling, inflammation, tumorigenesis, and interactions with pathogens. Recently, it was demonstrated that certain chemokines require interactions with GAGs for their in vivo function. The GAG interaction is thought to provide a mechanism for retaining chemokines on cell surfaces, facilitating the formation of chemokine gradients. These gradients serve as directional cues to guide the migration of the appropriate cells in the context of their inflammatory, developmental, and homeostatic functions. In this review, we discuss GAGs and their interaction with proteins, with a special emphasis on the chemokine system.

A Non-Glycosaminoglycan-Binding Variant of CC Chemokine Ligand 7 (Monocyte Chemoattractant Protein-3) Antagonizes Chemokine-Mediated Inflammation

A non-glycosaminoglycan (GAG)-binding variant of the pleiotropic chemokine CCL7 was generated by mutating to alanine the basic (B) amino acids within an identified (44)BXBXXB(49) GAG-binding motif. Unlike wild-type (wt) CCL7, the mutant sequence had no affinity for heparin. However, the mutant retained a normal affinity for CCR1, CCR2b, and CCR3, and produced a normal calcium flux in mononuclear leukocytes. Both the wt and mutant proteins elicited an equal leukocyte chemotactic response within a solute diffusion gradient but, unlike the wt protein, the mutant failed to stimulate cell migration across a model endothelium. The number of leukocytes recruited to murine air pouches by the mutant sequence was lower than that recruited by wt CCL7. Furthermore, the presence of a mixture of a mutant and wt CCL7 within the air pouch elicited no significant cell accumulation. Cell recruitment also failed using a receptor-sharing mixture of mutant CCL7 and wt CCL5 or a nonreceptor sharing mixture of mutant CCL7 and wt CXCL12. The potential of the mutant sequence to modulate inflammation was confirmed by demonstration of its ability to inhibit the chemotactic response generated in vitro by synovial fluid from patients with active rheumatoid arthritis. A further series of experiments suggested that the non-GAG-binding mutant protein could potentially induce receptor desensitization before, and at a site remote from, any physiological recognition of GAG-bound chemokines. These data demonstrate that GAG binding is required for chemokine-driven inflammation in vivo and also suggest that a non-GAG-binding chemokine receptor agonist can inhibit the normal vectorial leukocyte migration mediated by chemokines.

Interaction of chemokines and glycosaminoglycans: a new twist in the regulation of chemokine function with opportunities for therapeutic intervention

Despite their key role in inflammation, the apparent redundancy in the chemokine system is often cited as an argument against probing chemokines as therapeutic targets for inflammation. However, this in vitro redundancy frequently does not translate to the in vivo situation, as exemplified by the use of specific receptor antagonists, ligand neutralizing or receptor blocking antibodies and gene-deleted mice in models of human disease. Specificity may be conferred onto the chemokine system by fine-tuning of responses both temporally and spatially through their highly specific interactions with glycosaminoglycans (GAGs). In this survey, we present evidence for specificity in the interaction and introduce emerging technologies that enable detailed assessment of protein-GAG interactions. Finally, we address the issue of exploitation of this interaction for therapeutic advantage.

Chemokines bind to sulfatides as revealed by surface plasmon resonance

Chemokines bind to sulfated cell surface glycosaminoglycans and thereby modulate signaling mediated by G-protein-coupled seven-transmembrane domain chemokine receptors. Similar to glycosaminoglycans, sulfated oligosaccharides are also exposed on the cell surface by sulfatides, a class of glycosphingolipids. We have now identified sulfated glycosphingolipids (sulfatides) as novel binding partners for chemokines. Using surface plasmon resonance (SPR), the binding of proinflammatory and homeostatic chemokines to glycosphingolipids, in particular sulfatides, was investigated. Chemokines were immobilized while glycosphingolipids or additional phospholipids incorporated into liposomes were applied as soluble analytes. A specific affinity of the chemokines MCP-1/CCL2, IL-8/CXCL8, SDF-1alpha/CXCL12, MIP-1alpha/CCL3 and MIP-1beta/CCL4 to the sulfatides SM4s, SM3, SM2a and SB2, SB1a was detected. No significant interactions with the chemokines were observed for gangliosides, neutral glycosphingolipids or phospholipids. Chemokine receptors have been associated with the detergent-insoluble fraction supposed to contain 'rafts', i.e., glycosphingolipid enriched microdomains of the cell surface. Accordingly, the data suggest that early chemokine receptor signaling may take place in the vicinity of sulfated glycosphingolipids on the cell surface, whereby these sulfatides could modulate the chemokine receptor-mediated cell activation signal.

The X-ray structure of RANTES: heparin-derived disaccharides allows the rational design of chemokine inhibitors

The biological activity of chemokines requires interactions with cell surface proteoglycans. We have determined the structure of the chemokine RANTES (regulated on activation normal T cell expressed) in the presence of heparin-derived disaccharide analogs by X-ray crystallography. These structures confirm the essential role of the BBXB motif in the interaction between the chemokine and the disaccharide. Unexpected interactions were observed in the 30s loop and at the amino terminus. Mutant RANTES molecules were designed to abrogate these interactions and their biological activity examined in vivo. The K45E mutant within the BBXB motif lost the capacity to bind heparin and the ability to elicit cellular recruitment. The Y3A mutant maintained its capacity to bind heparin but was unable to elicit cellular recruitment. Finally, a tetrasaccharide is the smallest oligosaccharide which effectively abolishes the ability of RANTES to recruit cells in vivo. These crystallographic structures provide a description of the molecular interaction of a chemokine with glycosaminoglycans.

Lectin KM+-induced neutrophil haptotaxis involves binding to laminin

The lectin KM+ from Artocarpus integrifolia, also known as artocarpin, induces neutrophil migration by haptotaxis. The interactions of KM+ with both the extracellular matrix (ECM) and neutrophils depend on the lectin ability to recognize mannose-containing glycans. Here, we report the binding of KM+ to laminin and demonstrate that this interaction potentiates the KM+-induced neutrophil migration. Labeling of lung tissue by KM+ located its ligands on the endothelial cells, in the basement membrane, in the alveolus, and in the interstitial connective tissue. Such labeling was inhibited by 400 mM D-mannose, 10 mM Manalpha1-3[Manalpha1-6]Man or 10 microM peroxidase (a glycoprotein-containing mannosyl heptasaccharide). Laminin is a tissue ligand for KM+, since both KM+ and anti-laminin antibodies not only reacted with the same high molecular mass components of a lung extract, but also determined colocalized labeling in basement membranes of the lung tissue. The relevance of the KM+-laminin interaction to the KM+ property of inducing neutrophil migration was evaluated. The inability of low concentrations of soluble KM+ to induce human neutrophil migration was reversed by coating the microchamber filter with laminin. So, the interaction of KM+ with laminin promotes the formation of a substrate-bound KM+ gradient that is able to induce neutrophil haptotaxis.

Soluble mimics of a chemokine receptor: chemokine binding by receptor elements juxtaposed on a soluble scaffold

Despite the broad biological importance of G protein-coupled receptors (GPCRs), ligand recognition by GPCRs remains poorly understood. To explore the roles of GPCR extracellular elements in ligand binding and to provide a tractable system for structural analyses of GPCR/ligand interactions, we have developed a soluble protein that mimics ligand recognition by a GPCR. This receptor analog, dubbed CROSS5, consists of the N-terminal and third extracellular loop regions of CC chemokine receptor 3 (CCR3) displayed on the surface of a small soluble protein, the B1 domain of Streptococcal protein G. CROSS5 binds to the CCR3 ligand eotaxin with a dissociation equilibrium constant of 2.9 +/- 0.8 microM and competes with CCR3 for eotaxin binding. Control proteins indicate that juxtaposition of both CCR3 elements is required for optimal binding to eotaxin. Moreover, the affinities of CROSS5 for a series of eotaxin mutants are highly correlated with the apparent affinities of CCR3 for the same mutants, demonstrating that CROSS5 uses many of the same interactions as does the native receptor. The strategy used to develop CROSS5 could be applied to many other GPCRs, with a variety of potential applications.