The chemokine system as a therapeutic target in autoimmune thyroid diseases: a focus on the interferon-γ inducible chemokines and their receptor

The recruitment, trafficking, and in situ maintenance of specific subsets of activated lymphocytes constitute crucial steps for the initiation and perpetuation of chronic autoimmune inflammation. The fact that, after IFN-γ stimulation, thyrocytes secrete CXCR3- binding chemokines, which in turn recruits Th1 lymphocytes expressing CXCR3 and secreting IFN-γ, strongly supports the concept that the interferon-γ inducible chemokines (CXCL9, CXCL10, and CXCL11) and their receptor CXCR3 play an important role in the initiation of autoimmune thyroid diseases (AITD). Thus, interfering with CXCR3 might result in the abrogation of the inflammatory process. The understanding of these pathogenetic mechanisms suggested novel therapeutic approaches, with a growing interest for finding a way to interrupt the interactions between chemokines and their receptors. In this review, we focus on the efforts performed in establishing new pharmacological compounds able to target the chemokine/chemokine receptors system as well as to prevent the secretion of CXCR3-binding chemokines, induced by pro-inflammatory cytokines. The crucial issue of selecting the relevant therapeutic targets in animal models of AITD was also discussed. Although some encouraging results have been reached, major hurdles were encountered on the way to success. As a result, we are still waiting for the first anti-chemokine anti-inflammatory drug. Given the importance of leukocytes recruitment to inflammatory sites, research will continue to address the issue of developing specific chemokine-receptor antagonists. We look forward to the development of these novel pharmacological compounds which will hopefully provide a more valid alternative to the currently used lifelong replacement therapies for AITD.     

Chemokine receptors in chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) is a debilitating disease characterized by recurrent episodes of leukocyte infiltration in the lung parenchyma causing progressive pulmonary tissue damage and loss of function. Recruitment of neutrophils and CD8+ T cells is linked to disease progression and is under control of chemotactic mediators produced in the inflamed COPD lung. Recent progress in elucidation of the molecular mechanisms that regulate migration of inflammatory cells into the lung has revealed interesting novel targets for therapeutic intervention in this disease. Chemokine receptors CXCR1 and CXCR2 expressed on neutrophils and CXCR3 expressed on CD8+ T cells have been identified as potential therapeutic targets to prevent recruitment of pathogenic cells into the inflamed lung. However, the observation that chemokine receptors are also expressed and functional on various types of lung resident cells including epithelial and smooth muscle cells has raised new questions on the role played by chemokine receptors in COPD. These new findings suggest that chemokine receptor signalling could contribute to the adaptive response of lung tissue resident cells to the microenvironmental changes induced by inflammation. Thus, investigation of the role played by chemokine receptors in development of COPD remains a fertile area of research. Nevertheless, validation of chemokine receptor targets in COPD has proven a difficult challenge given the lack of predictive animal models of the disease and the still poorly defined etiology and pathogenesis.     

CCR9 and inflammatory bowel disease

Background: The pathological features of inflammatory bowel disease (IBD) are associated with leukocyte cell infiltrates, which contribute to disease progression and persistence by production of proinflammatory mediators. Recruiting leukocytes to the gut involves local expression of chemokines that interact with receptors on the leukocytes' surface. Specific antagonists may interfere with leukocyte recruitment to the intestine. The chemokine receptor CCR9 is one of the key molecules in leukocyte homing to gut mucosa. CCR9 antagonists have been shown to retard progression in patients with IBD. Objective: To discuss CCR9 as a potential target for the treatment of IBD. Methods: A literature review. Results/conclusions: The therapeutic effects of CCR9 antagonists, in combination with established therapies, should be evaluated in an attempt to slow down leukocyte recruitment at early stages of IBD.     

Broad spectrum chemokine inhibitors related to NR58-3.14.3

The chemokine family consists of more than 50 structurally-related small proteins which signal through type 1 G-protein coupled receptors (GPCRs) to regulate a range of immune functions, with particular focus on regulating leukocyte trafficking. They have been implicated both in normal physiological leukocyte traffic, and in recruitment of leukocytes to sites of pathological inflammation. As a result, chemokine inhibitors may have useful anti-inflammatory therapeutic properties in vivo. Compounds with chemokine-inhibitory properties that have been described to date, fall into two broad categories: receptor-specific antagonists which block the action of one or a small number of related chemokines, and broad-spectrum chemokine inhibitors (BSCIs) which block leukocyte migration in response to many, if not all, chemokines simultaneously. Since many chemokines apparently show functional redundancy in vivo, the BSCI class are attractive candidates for development as anti-inflammatory therapies. Here, we review the development of BSCIs, with particular focus on the design and characterisation of non-peptide compounds. The key structural requirements for BSCI activity are discussed, together with their implications for the mechanism of BSCI action.     

Broad-spectrum chemokine inhibitors (BSCIs) and their anti-inflammatory effects in vivo

Inappropriate inflammation is a component of a wide range of human diseases, including autoimmune disease, atherosclerosis, osteoporosis and Alzheimer's disease. Chemokines play an important role in orchestrating leukocyte recruitment during inflammation, and therefore represent an important target for anti-inflammatory therapies. Unfortunately, the chemokine system is complex, with about 50 ligands and 20 receptors, often acting with redundancy, making selection of appropriate specific antagonists difficult. One approach to overcoming this difficulty may be the development of broad-spectrum chemokine inhibitors (BSCIs). Here we review the present state of knowledge on BSCIs, including their activity in vitro and their anti-inflammatory effects in vivo, and discuss the future development of BSCIs as anti-inflammatory therapies for use in the clinic.     

Agents against cytokine synthesis or receptors

Various cytokines play a critical role in pathophysiology of chronic inflammatory lung diseases including asthma and chronic obstructive pulmonary disease (COPD). The increasing evidence of the involvement of these cytokines in the development of airway inflammation raises the possibility that these cytokines may become the novel promising therapeutic targets. Studies concerning the inhibition of interleukin (IL)-4 have been discontinued despite promising early results in asthma. Although blocking antibody against IL-5 markedly reduces the infiltration of eosinophils in peripheral blood and airway, it does not seem to be effective in symptomatic asthma, while blocking IL-13 might be more effective. On the contrary, anti-inflammatory cytokines themselves such as IL-10, IL-12, IL-18, IL-23 and interferon-gamma may have a therapeutic potential. Inhibition of TNF-alpha may also be useful in severe asthma or COPD. Many chemokines are also involved in the inflammatory response of asthma and COPD through the recruitment of inflammatory cells. Several small molecule inhibitors of chemokine receptors are now in development for the treatment of asthma and COPD. Antibodies that block IL-8 reduce neutrophilic inflammation. Chemokine CC3 receptor antagonists, which block eosinophil chemotaxis, are now in clinical development for asthma therapy. As many cytokines are involved in the pathophysiology of inflammatory lung diseases, inhibitory agents of the synthesis of multiple cytokines may be more useful tools. Several such agents are now in clinical development.     

CC-chemokine receptors in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of mortality and disability in the world, with a prevalence that is expected to increase in the next decades. The disease is characterized by a chronic inflammatory response of the airways and lungs to noxious particles and gases, mostly cigarette smoke. The molecular and cellular mechanisms that lead to this exaggerated influx of cells belonging to both the innate and adaptive immune system are not yet completely unravelled. However, there is now growing evidence that the recruitment of these inflammatory cells in response to cigarette smoke is largely regulated by chemokines acting as ligands for chemokine receptors. Several of these receptors, which fall mainly in the CC- or CXC-category, have been implicated in the pathogenesis of COPD. In this review we will focus mainly on the CC-family, as the involvement of CXC-receptors in COPD has already been extensively reviewed. In patients with COPD, several CC-chemokines like MIP-1alpha, MIP-3alpha, RANTES and MCP-1 are upregulated, suggesting the contribution of their respective receptor in the pathogenesis of the disease. Using knock out mice, this contribution has been further confirmed for CCR5 and CCR6, evidenced by an attenuated accumulation of inflammatory cells like macrophages, dendritic cells, neutrophils and CD8(+) T-lymphocytes upon cigarette smoke-exposure. Moreover, mice deficient for CCR5 or CCR6 are partially protected from the development of pulmonary emphysema, another hallmark of COPD. These data suggest that chemokine receptors are potential therapeutic targets to reduce the chronic inflammation and parenchymal destruction in COPD.     

Chemokines and atherosclerotic plaque progression: towards therapeutic targeting?

Atherosclerosis is currently viewed as an inflammatory disease in which the initiation and progression of the atherosclerotic plaque towards a rupture prone, unstable plaque is driven by leukocyte recruitment mediated by various inflammatory mediators. Recently, interest in chemotactic cytokines or chemokines with regard to atherosclerosis has been growing as chemokines mediate the influx of leukocytes that is typical of atherothrombosis. The activity of the majority of chemokines is overlapping and chemokines are not only produced by the various cellular constituents of the atherosclerotic plaque but also by activated platelets. Consequently, the direct influence of individual chemokines on plaque destabilisation and rupture is widespread and rather unclear. Experimental research has already established the role of a number of chemokines in advanced atherosclerosis. Nevertheless, given the complexity and size of the chemokine family, further screening of cardiovascular disease for chemokine level and genetic polymorphisms for chemokines will be warranted as the search for viable biomarkers of plaque destabilization as well as novel therapeutic targets for specific atheroregressive therapeutic compounds is ongoing. With regard to the latter, clinical trials with specific chemokine inhibitory strategies, like chemokine receptor antagonists, are already underway in other inflammatory disorders. Summarizing, chemokine inhibition likely constitutes an important therapeutic option next to already established drugs in the management of cardiovascular disease.     

以趋化因子受体为靶点的抗哮喘小分子药物研究进展

哮喘是一种以气道炎症、气道高反应性及气道重塑为特征并伴随支气管炎性细胞浸润的慢性呼吸道疾病。趋化因子通过与趋化因子受体结合介导炎性细胞向支气管迁移,在哮喘发病中起着重要的作用。以趋化因子及其受体为靶点是目前抗炎、抗哮喘药物研究的热点。本文主要针对近年来趋化因子受体的小分子拮抗剂在抗哮喘方面的研究成果予以综述,将有助于抗哮喘药物设计,为进一步研究提供参考。     

A distinct subset of chemokines dominates the mucosal chemokine response in inflammatory bowel disease

BACKGROUND: Inflammatory bowel disease (IBD) is characterised by intense mucosal recruitment of activated leukocytes. Chemokines determine inflammatory leukocyte recruitment and retention. AIM: To compare expression of the entire chemokine family within colonic mucosa from IBD patients and uninflamed controls. METHODS: A microarray of cDNAs, representing every member of this superfamily and their cognate receptors, was hybridised with probes derived from colonoscopic biopsies. RESULTS: A distinct subset of chemokines, consisting of CXCLs 1-3 and 8 and CCL20, was upregulated in active colonic IBD, compared with uninflamed areas or tissue from controls. Increased expression of their cognate receptors, CXCR1, CXCR2 and CCR6, was confirmed by quantitative PCR and immunohistochemistry. An identical chemokine response was induced in Caco-2 cells by stimulation with interleukin (IL)-1beta, but not tumour necrosis factor-alpha (TNF-alpha). By contrast, IL-1beta and TNF-alpha were synergistic in an HT29 cell line and primary keratinocytes. CONCLUSIONS: IL-1beta and TNF-alpha appear to be the pivotal mediators of a previously unidentified coordinated epithelial chemokine response that dominates the mucosal chemokine environment in inflamed IBD tissue.     

Macrophage inflammatory protein 1 and CCR5 as attractive therapeutic targets for HIV infection

Chemokines play key roles in inflammatory and immune responses mediated by their respective target cell populations. For instance, release of chemokines from inflammatory cells is a crucial step in the recruitment of cells needed to establish local inflammatory responses (e.g. rheumatoid arthritis). Moreover, recent advances in our understanding of the pathogenesis of human immunodeficiency virus (HIV) infection have revealed that chemokines and chemokine receptors are crucially involved in the molecular mechanism of HIV entry into target cells. Studies have shown that the chemokine receptor CCR5 serves as a critical coreceptor during the viral entry stage of HIV infection, while its ligands macrophage inflammatory protein (MIP)-1alpha and beta and RANTES act as endogenous inhibitors of HIV infection. This makes chemokine/chemokine receptor systems an attractive potential target for the development highly specific drugs with which to improve the management of HIV. This review will discuss the latest developments in the research on chemokine/chemokine receptor systems, especially MIP-1 and CCR5, with a particular focus on their role in the mechanism of HIV infection and on the development of effective therapies against acquired immunodeficiency syndrome (AIDS).     

Chemokine receptors as specific anti-inflammatory targets in peripheral nerves

Chemokines are the initial mediators of leukocyte migration across concentration gradients in vitro and to sites of inflammation in vivo. Chemokines signal via specific seven-transmembrane spanning G-protein coupled receptors (GPCRs). About 50 chemokine ligands and 18 receptors have been identified to date, and several are involved in leukocyte trafficking in human inflammation. Several chemokines signal via a single receptor, while others signal via multiple receptors. This redundancy may be necessary to mediate essential biological processes in vivo. There is evidence that specific chemokines and their receptors are expressed in the peripheral nerves or cerebrospinal fluid of patients with autoimmune neuropathies such as Guillain-Barré syndrome and Chronic Inflammatory Demyelinating Polyradiculoneuropathy and their animal models. Hematogenous leukocyte trafficking and chemokine-mediated signaling has also been implicated in the generation of neuropathic pain following peripheral nerve injury. Chemokine receptors, being GPCRs, provide an attractive drug target for modulating the harmful effects of peripheral nerve inflammation. The efficacy of anti-inflammatory therapies, including treatments that restrict leukocyte migration, has been established in several inflammatory disorders such as multiple sclerosis. There are several ongoing clinical trials testing chemokine receptor antagonists as specific anti-inflammatory drugs. This review evaluates the current status of the chemokine biology of peripheral neuropathies, highlighting areas where further studies are needed and discusses potentially selective drug targets for peripheral nerve inflammation and neuropathic pain.     

Emerging drugs for asthma

Background: Current therapies for asthma are aimed at controlling disease symptoms and for the majority of asthmatics inhaled corticosteroid anti-inflammatory therapy is effective. However, this approach requires life-time therapy while a subset of patients remains symptomatic despite optimal treatment creating a clear unmet medical need. Objectives: It is recognised that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches may identify new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach may provide disease-modifying treatments. Results: Significant areas of drug development include humanised monoclonal antibodies (mAb) for asthma therapy including those against IgE, IL-4 and IL-5. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include the use of humanised receptor blocking mAb or the removal of cytokines or chemokines via their binding to soluble receptor constructs. Small-molecule receptor antagonists also target receptors or the cellular signal transduction pathways that are activated following cytokine or chemokine receptor ligation. Another approach is to target asthma relevant mediators or the pathways controlling pro-inflammatory leukocyte accumulation within the asthmatic lung. Conclusions: This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy. Current therapies for asthma are aimed at controlling disease symptoms, and for the majority of asthmatics inhaled corticosteroid anti-inflammatory therapy is effective. However, this approach requires lifetime therapy; and a subset of patients remains symptomatic despite optimal treatment, creating a clear unmet medical need. It is recognised that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches may identify new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach may provide disease-modifying treatments. Significant areas of drug development include humanised mAb for asthma therapy, including those against IgE, IL-4 and IL-5. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include the use of humanised receptor blocking mAb or the removal of cytokines or chemokines via their binding to soluble receptor constructs. Small-molecule receptor antagonists also target receptors or the cellular signal transduction pathways that are activated following cytokine or chemokine receptor ligation. Another approach is to target asthma-relevant mediators, or the pathways controlling pro-inflammatory leukocyte accumulation within the asthmatic lung. This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy.     

Frontrunners in novel pharmacotherapy of COPD

The mainstay of current drug therapy is long-acting bronchodilators; several longer acting inhaled beta(2)-agonists and muscarinic antagonists (and combinations) are now in development. No treatments reduce the progression or suppress the inflammation of COPD. With better understanding of the inflammatory and destructive process, several new targets have been identified. Several mediator antagonists tested in COPD have been disappointing, but of CXCR2 antagonists that block pulmonary neutrophil and monocyte recruitment may be more promising. Broad spectrum anti-inflammatory drugs may be more effective, and include inhibitors of PDE4, p38 MAPK and NF-kappaB, but side effects will be a major limitation so that inhaled delivery will be necessary. Perhaps the most promising approach is reversal corticosteroid resistance through increasing HDAC2 activity. This may be achieved by theophylline-like drugs, more effective antioxidants and non-antibiotic macrolides.     

Chemokine receptor inhibitors as a novel option in treatment of asthma

The migration of cells towards and into the site of an inflammatory insult is critical for maintenance of the inflammatory response and its resolution. This is particularly so in the case of asthma where recruitment of key effector cells may control disease severity, responsiveness to current therapies and the airway remodelling associated with the disease. Chemokine receptor antagonists have the hope of preventing inflammatory cell recruitment to the airway and perhaps as a consequence affect the resolution of airway remodelling. A number of selective antagonists directed at various CC and CXC receptors thought to be important in asthma are currently at various stages of clinical development. Results from these studies will determine whether chemokine receptor antagonists will prove beneficial in severe glucocorticoid-dependent and -resistant asthmatic subjects. Furthermore, it is possible that early treatment with these agents may prevent the disease from becoming established.     

Blockade of chemokine-mediated tissue injury in lupus nephritis

Pro-inflammatory chemokines are important mediators of inflammation and autoimmune injury. The spatial and temporal expression of chemokines and chemokine receptors in the nephritic kidney suggests that targeting the chemokine system may represent a valuable approach for anti-inflammatory therapy of lupus nephritis. In this review we summarize the available data on the pathogenic role of chemokines and chemokine receptors in lupus nephritis and particularly focus on epidemiological data in lupus patients and interventional studies with chemokine or chemokine receptor antagonists in experimental lupus.     

Review article: Chemokine production by intestinal epithelial cells: a therapeutic target in inflammatory bowel disease?

The intestinal epithelium plays an important role in the recognition of pathogenic organisms and in the recruitment of inflammatory cells to the mucosa. Epithelial chemokine production may constitute a key target in future therapies for inflammatory bowel disease (IBD). Chemokines are divided into two subfamilies, the C-C family and C-X-C family. Most C-C chemokines target mononuclear cells and many C-X-C chemokines attract neutrophils. Interleukin-8 (IL-8), a C-X-C chemokine, acts as a motor for the recruitment of neutrophils into the non-inflamed mucosa and is present in both enterocytes and mucosal inflammatory cells. Epithelial cells may be the first to signal the presence of pathogens, as well as contributing to IL-8 production in IBD. Data have also shown that intestinal epithelial cells are able to respond to IL-1β and tumour necrosis factor-alpha (TNF-α) at concentrations known to occur in the inflamed mucosa. Monocyte chemotactic protein-1 (MCP-1), a member of the C-C chemokine family, is noticeably increased in IBD. These data show that C-X-C and C-C chemokines are equally important properties of mucosal epithelial cells. The effects of two anti-inflammatory drugs (dexamethasone and cyclosporin) on chemokine production are significantly different and this provides a rationale for combination therapy.     

Identification and profiling of CXCR3–CXCR4 chemokine receptor heteromer complexes

Background and Purpose

The C-X-C chemokine receptors 3 (CXCR3) and C-X-C chemokine receptors 4 (CXCR4) are involved in various autoimmune diseases and cancers. Small antagonists have previously been shown to cross-inhibit chemokine binding to CXCR4, CC chemokine receptors 2 (CCR2) and 5 (CCR5) heteromers. We investigated whether CXCR3 and CXCR4 can form heteromeric complexes and the binding characteristics of chemokines and small ligand compounds to these chemokine receptor heteromers.

Experimental Approach

CXCR3–CXCR4 heteromers were identified in HEK293T cells using co-immunoprecipitation, time-resolved fluorescence resonance energy transfer, saturation BRET and the GPCR-heteromer identification technology (HIT) approach. Equilibrium competition binding and dissociation experiments were performed to detect negative binding cooperativity.

Key Results

We provide evidence that chemokine receptors CXCR3 and CXCR4 form heteromeric complexes in HEK293T cells. Chemokine binding was mutually exclusive on membranes co-expressing CXCR3 and CXCR4 as revealed by equilibrium competition binding and dissociation experiments. The small CXCR3 agonist VUF10661 impaired binding of CXCL12 to CXCR4, whereas small antagonists were unable to cross-inhibit chemokine binding to the other chemokine receptor. In contrast, negative binding cooperativity between CXCR3 and CXCR4 chemokines was not observed in intact cells. However, using the GPCR-HIT approach, we have evidence for specific β-arrestin2 recruitment to CXCR3-CXCR4 heteromers in response to agonist stimulation.

Conclusions and Implications

This study indicates that heteromeric CXCR3–CXCR4 complexes may act as functional units in living cells, which potentially open up novel therapeutic opportunities.     

Site-directed mutagenesis of the CC chemokine binding protein 35K-Fc reveals residues essential for activity and mutations that increase the potency of CC chemokine blockade

Chemokines of the CC class are key mediators of monocyte recruitment and macrophage differentiation and have a well documented role in many inflammatory diseases. Blockade of chemokine activity is therefore an attractive target for anti-inflammatory therapy. 35K (vCCI) is a high-affinity chemokine binding protein expressed by poxviruses, which binds all human and murine CC chemokines, preventing their interaction with chemokine receptors. We developed an Fc-fusion protein of 35K with a modified human IgG1 Fc domain and expressed this construct in human embryonic kidney 293T cells. Purified 35K-Fc is capable of inhibiting CC chemokine-induced calcium flux, chemotaxis, and β-arrestin recruitment in primary macrophages and transfected cells. To elucidate the residues involved in chemokine neutralization, we performed site-directed mutagenesis of six key amino acids in 35K and expressed the mutant Fc-fusion proteins in vitro. We screened the mutants for their ability to block chemokine-induced β-arrestin recruitment in transfected cells and to inhibit primary macrophage signaling in an electric cell substrate impedance sensing assay. Using a sterile model of acute inflammation, zymosan-induced peritonitis, we confirmed that wild-type 35K-Fc can reduce monocyte recruitment, whereas one mutant (R89A) showed a more pronounced blockade of monocyte influx and another mutant (E143K) showed total loss of function. We believe that 35K-Fc will be a useful tool for exploring the role of CC chemokines in chronic inflammatory pathologies, and we have identified a higher potency form of the molecule that may have potential therapeutic applications in chronic inflammatory disease.