Strategies for chemokine antagonists as therapeutics

Blocking CCL5-CXCL4 heteromerization preserves heart function after myocardial infarction by attenuating leukocyte recruitment and NETosis

Myocardial infarction (MI) is a major cause of death in Western countries and finding new strategies for its prevention and treatment is thus of high priority. In a previous study, we have demonstrated a pathophysiologic relevance for the heterophilic interaction of CCL5 and CXCL4 in the progression of atherosclerosis. A specifically designed compound (MKEY) to block this CCL5-CXCR4 interaction is investigated as a potential therapeutic in a model of myocardial ischemia/reperfusion (I/R) damage. 8 week-old male C57BL/6 mice were intravenously treated with MKEY or scrambled control (sMKEY) from 1 day before, until up to 7 days after I/R. By using echocardiography and intraventricular pressure measurements, MKEY treatment resulted in a significant decrease in infarction size and preserved heart function as compared to sMKEY-treated animals. Moreover, MKEY treatment significantly reduced the inflammatory reaction following I/R, as revealed by specific staining for neutrophils and monocyte/macrophages. Interestingly, MKEY treatment led to a significant reduction of citrullinated histone 3 in the infarcted tissue, showing that MKEY can prevent neutrophil extracellular trap formation in vivo. Disrupting chemokine heterodimers during myocardial I/R might have clinical benefits, preserving the therapeutic benefit of blocking specific chemokines, and in addition, reducing the inflammatory side effects maintaining normal immune defence.

Conformational analysis of the human chemokine receptor CXCR3

In the last years, some studies showed the patho-genetic role of CXCR3 bound to its ligands in many human inflammatory diseases and cancers. Thus, the blockage of the CXCR3 interaction site to its ligands is seen as a possible therapeutic target for the treatment of cancer. The presence of flexible regions in the chemokine receptors determines their capability to develop specific mechanisms of action. We have recently focused on the features of the N-terminal region of human CXCR3 free in solution, where we demonstrate the presence of numerous conformational ensembles, dynamically stabilized by H-bonds. Since up to now no structure was experimentally determined for CXCR3, we decided to approach the study of its conformational behavior by molecular dynamics simulations, in a lipid bilayer, surrounded of water, at neutral pH and 300K. Furthermore, we modeled the CXCR3/CXCL11 complex, where CXCL11 is one of its natural ligands. The aim of this work is to have a vision as realistic as possible in dynamic terms of the biological mechanism that drives the search for the ligand, its interaction and the formation of a stable complex between CXCR3 and CXCL11. Overall, our approach has been able to describe the structural events which dynamically characterize the molecular mechanisms involved in the binding of CXCR3 to CXCL11 and the critical role exerted by its N-terminal region in "hunting" and capturing the ligand.

Changes in gene expression induced by histamine, fexofenadine and osthole: Expression of histamine H1 receptor, COX-2, NF-κB, CCR1, chemokine CCL5/RANTES and interleukin-1β in PBMC allergic and non-allergic patients

INTRODUCTION

Fexofenadine (FXF) is a third-generation antihistamine drug and osthole is assumed as a natural antihistamine alternative. This paper compares results of histamine, FXF and osthole impact on HRH-1, COX-2, NF-κB-p50, CCR1 mRNA expression. We also measured mRNA expression of IL-1β and CCL5/RANTES in incubated peripheral blood mononuclear cells (PBMC) to compared how histamine, FXF and osthole had influence on expression level and interacts on product secretion.

OBJECTIVE

The purpose was to investigate expression pattern in asthma PBMC.

METHODS

The cultures were treated 72h with FXF and osthole. We measured mRNA expression of histamine HRH-1, COX-2, NF-κB-p50, CCR1, IL-1β and CCL5/RANTES with Real-Time PCR (RT-PCR).

RESULTS

The present study suggest that osthole may be a potential inhibitor of histamine H₁ receptor activity. We also demonstrated that cells cultured with histamine increase COX-2 mRNA expression and osthole reduce it.

CONCLUSION

Allergy remains one of the most common chronic diseases in Europe and it is rapidly approaching epidemic proportions; with current predictions estimating that the number of allergy-afflicted will equal the healthy population by 2020. It is therefore paramount to find new pharmaceuticals which successfully combat allergic disease.

Modulation of Chemokine Responses: Synergy and Cooperativity

Chemokine biology is mediated by more complex interactions than simple monomolecular ligand–receptor interactions, as chemokines can form higher order quaternary structures, which can also be formed after binding to glycosaminoglycans (GAGs) on endothelial cells, and their receptors are found as dimers and/or oligomers at the cell surface. Due to the complexity of the chemokine binding and signaling system, several mechanisms have been proposed to provide an explanation for the synergy observed between chemokines in leukocyte migration. Pioneering studies on interactions between different chemokines have revealed that they can act as antagonists, or synergize with other chemokines. The synergism can occur at different levels, involving either two chemokine receptors triggered simultaneously or sequentially exposed to their agonists, or the activation of one type of chemokine receptor triggered by chemokine heterocomplexes. In addition to the several chemokines that, by forming a heterocomplex with chemokine receptor agonists, act as enhancers of molecules of the same family, we have recently identified HMGB1, an endogenous damage-associated molecular patterns (DAMPs) molecule, as an enhancer of the activity of CXCL12. It is now evident that synergism between chemokines is crucial at the very early stage of inflammation. In addition, the low-affinity interaction with GAGs has recently been shown to induce cooperativity allowing synergy or inhibition of activity by displacement of other ligands.

Primed Mycobacterial Uveitis (PMU): Histologic and Cytokine Characterization of a Model of Uveitis in Rats

PURPOSE

The purpose of this study was to compare the histologic features and cytokine profiles of experimental autoimmune uveitis (EAU) and a primed mycobacterial uveitis (PMU) model in rats.

METHODS

In Lewis rats, EAU was induced by immunization with interphotoreceptor binding protein peptide, and PMU was induced by immunization with a killed mycobacterial extract followed by intravitreal injection of the same extract. Clinical course, histology, and the cytokine profiles of the aqueous and vitreous were compared using multiplex bead fluorescence immunoassays.

RESULTS

Primed mycobacterial uveitis generates inflammation 2 days after intravitreal injection and resolves spontaneously 14 days later. CD68+ lymphocytes are the predominant infiltrating cells and are found in the anterior chamber, surrounding the ciliary body and in the vitreous. In contrast to EAU, no choroidal infiltration or retinal destruction is noted. At the day of peak inflammation, C-X-C motif ligand 10 (CXCL10), IL-1β, IL-18, and leptin were induced in the aqueous of both models. Interleukin-6 was induced 2-fold in the aqueous of PMU but not EAU. Cytokines elevated in the aqueous of EAU exclusively include regulated on activation, normal T cell expressed and secreted (RANTES), lipopolysaccharide-induced CXC chemokine (LIX), growth-related oncogene/keratinocyte chemokine (GRO/KC), VEGF, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), and IL-17A. In the vitreous, CXCL10, GRO/KC, RANTES, and MIP-1α were elevated in both models. Interleukin-17A and IL-18 were elevated exclusively in EAU.

CONCLUSIONS

Primed mycobacterial uveitis generates an acute anterior and intermediate uveitis without retinal involvement. Primed mycobacterial uveitis has a distinct proinflammatory cytokine profile compared with EAU, suggesting PMU is a good complementary model for study of immune-mediated uveitis. CXCL10, a proinflammatory cytokine, was increased in the aqueous and vitreous of both models and may be a viable therapeutic target.

Fractalkine receptor polymorphism may not be associated with the development and clinical course of ulcerative colitis

Fractalkine (CX3C), a chemokine expressed by epithelial cells within normal and inflamed colorectal mucosa, induces leukocyte adhesion and migration via fractalkine receptor. The aim of this study was to investigate two single nucleotide polymorphisms of the fractalkine receptor gene as a risk factor both for the development and clinical findings of ulcerative colitis. In this study, 51 patients with ulcerative colitis (UC) and 80 controls were recruited. Genotypes of fractalkine receptorc.745G>A (V249I) and c.839C>T (T280M) polymorphisms were identified by restriction fragment length polymorphism analyses after polymerase chain reaction.Genotype distribution and allele frequencies of V249I and T280M were not statistically significantly different between UC and control groups (p>0.05). No statistically significant relationship was found between fractalkine receptor polymorphisms and clinical findings of UC. We observed no significant difference in fractalkine receptor polymorphism between patients and control group and no genotype-phenotype relation. Therefore, we concluded that fractalkine receptor polymorphisms may not contribute to the molecular pathogenesis of UC.

Chemokines and cytokines as salivary biomarkers for the early diagnosis of oral cancer

Chemokines have been shown to be important in both inflammation and carcinogenesis and are able to be measured in saliva with relatively robust methods including enzyme-linked immunosorbent assays (ELISA). Thus it has been hypothesized that patients with oral cancer and oral potentially malignant lesions will have elevated levels of specific chemokines in oral fluids and that this may be used as a marker of both the early detection of malignant disease and progression to malignancy. The concept that salivary biomarkers can be easily measured and indicate disease states has profound consequences for clinical practice and may open up new strategies for the diagnosis, prognosis, and potential therapy of oral squamous cell carcinoma (OSCC). This review focuses on our understanding of cytokines and chemokines and the potential role that they may have in clinical practice.

Chemokine (C-X-C motif) ligand (CXCL)10 in autoimmune diseases

(C-X-C motif) ligand (CXCL)10 (CXCL10) belongs to the ELR(-) CXC subfamily chemokine. CXCL10 exerts its function through binding to chemokine (C-X-C motif) receptor 3 (CXCR3), a seven trans-membrane receptor coupled to G proteins. CXCL10 and its receptor, CXCR3, appear to contribute to the pathogenesis of many autoimmune diseases, organ specific (such as type 1 diabetes, autoimmune thyroiditis, Graves' disease and ophthalmopathy), or systemic (such as rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, mixed cryoglobulinemia, Sjögren syndrome, or systemic sclerosis). The secretion of CXCL10 by cluster of differentiation (CD)4+, CD8+, natural killer (NK) and NK-T cells is dependent on interferon (IFN)-γ, which is itself mediated by the interleukin-12 cytokine family. Under the influence of IFN-γ, CXCL10 is secreted by several cell types including endothelial cells, fibroblasts, keratinocytes, thyrocytes, preadipocytes, etc. Determination of high level of CXCL10 in peripheral fluids is therefore a marker of host immune response, especially T helper (Th)1 orientated T-cells. In tissues, recruited Th1 lymphocytes may be responsible for enhanced IFN-γ and tumor necrosis factor-α production, which in turn stimulates CXCL10 secretion from a variety of cells, therefore creating an amplification feedback loop, and perpetuating the autoimmune process. Further studies are needed to investigate interactions between chemokines and cytokines in the pathogenesis of autoimmune diseases and to evaluate whether CXCL10 is a novel therapeutic target in various autoimmune diseases.

G protein-coupled receptors revisited: therapeutic applications inspired by synthetic biology

G protein-coupled receptors (GPCRs) mediate the majority of cellular responses to hormones and neurotransmitters within the human body. They have much potential in the emerging field of synthetic biology, which is the rational, systematic design of biological systems with desired functionality. The responsiveness of GPCRs to a plethora of endogenous and exogenous ligands and stimuli make them ideal sensory receptor modules of synthetic gene networks. Such networks can activate target gene expression in response to a specific stimulus. Additionally, because GPCRs are important pharmacological targets of various human diseases, genes encoding their protein/peptide ligands can also be incorporated as target genes of the response output elements of synthetic gene networks. This review aims to critically examine the potential role of GPCRs in constructing therapeutic synthetic gene networks and to discuss various challenges in utilizing GPCRs for synthetic biology applications.

An analysis of the function and expression of D6 on lymphatic endothelial cells

The mechanisms by which CC chemokine receptor (CCR)7 ligands are selectively presented on lymphatic endothelium in the presence of inflammatory chemokines are poorly understood. The chemokine-scavenging receptor D6 is expressed on lymphatic endothelial cells (LEC) and contributes to selective presentation of CCR7 ligands by suppressing inflammatory chemokine binding to LEC surfaces. As well as preventing inappropriate inflammatory cell attachment to LECs, D6 is specifically involved in regulating the ability of LEC to discriminate between mature and immature dendritic cells (DCs). D6 overexpression reduces immature DC (iDC) adhesion to LECs, whereas D6 knockdown increases adhesion of iDCs that displace mature DCs. LEC D6 expression is regulated by growth factors, cytokines, and tumor microenvironments. In particular, interleukin-6 and interferon-γ are potent inducers, indicating a preferential role for D6 in inflamed contexts. Expression of the viral interleukin-6 homolog from Kaposi sarcoma-associated herpesvirus is also sufficient to induce significant D6 upregulation both in vitro and in vivo, and Kaposi sarcoma and primary effusion lymphoma cells demonstrate high levels of D6 expression. We therefore propose that D6, which is upregulated in both inflammatory and tumor contexts, is an essential regulator of inflammatory leukocyte interactions with LECs and is required for immature/mature DC discrimination by LECs.

D6: the 'crowd controller' at the immune gateway

The chemokine-scavenging receptor, D6, is reported to regulate resolution of inflammatory responses. However, recent data also point to an unanticipated role for D6 in coordinating innate and adaptive immune responses. Here, we propose that D6 is essential for preventing inflammatory leukocyte association with lymphatic vasculature. In the absence of D6, inappropriate inflammatory leukocyte accumulation around lymphatic endothelium congests the lymphatic system, impairing fluid and cellular flow from inflamed sites to lymph nodes and reducing efficiency of antigen presentation. Thus, the inability of D6-deficient mice to resolve inflammation may be a byproduct of impaired fluid drainage from inflamed sites and thus we provide a model unifying D6 function in innate and adaptive immune responses.

Chemokine oligomerization in cell signaling and migration

Chemokines are small proteins best known for their role in controlling the migration of diverse cells, particularly leukocytes. Upon binding to their G-protein-coupled receptors on the leukocytes, chemokines stimulate the signaling events that cause cytoskeletal rearrangements involved in cell movement, and migration of the cells along chemokine gradients. Depending on the cell type, chemokines also induce many other types of cellular responses including those related to defense mechanisms, cell proliferation, survival, and development. Historically, most research efforts have focused on the interaction of chemokines with their receptors, where monomeric forms of the ligands are the functionally relevant state. More recently, however, the importance of chemokine interactions with cell surface glycosaminoglycans has come to light, and in most cases appears to involve oligomeric chemokine structures. This review summarizes existing knowledge relating to the structure and function of chemokine oligomers, and emerging methodology for determining structures of complex chemokine assemblies in the future.

Chemokine receptor oligomerization: a further step toward chemokine function

A broad array of biological responses including cell polarization, movement, immune and inflammatory responses, as well as prevention of HIV-1 infection, are triggered by the chemokines, a family of secreted and structurally related chemoattractant proteins that bind to class A-specific seven-transmembrane receptors linked to G proteins. Chemokines and their receptors should not be considered isolated entities, as they act in complex networks. Chemokines bind as oligomers, or oligomerize after binding to glycosaminoglycans on endothelial cells, and are then presented to their receptors on target cells, facilitating the generation of chemoattractant gradients. The chemokine receptors form homo- and heterodimers, as well as higher order structures at the cell surface. These structures are dynamic and are regulated by receptor expression and ligand levels. Complexity is even greater, as in addition to regulation by cytokines and decoy receptors, chemokine and receptor levels are affected by proteolytic cleavage and other protein modifications. This complex scenario should be considered when analyzing chemokine biology and the ability of their antagonists to act in vivo. Strategies based on blocking or stabilizing ligand and receptor dimers could be alternative approaches that might have broad therapeutic potential.

Repair after myocardial infarction, between fantasy and reality: the role of chemokines

Despite considerable progress over the last decades, acute myocardial infarction continues to remain the major cause of morbidity and mortality worldwide. The present therapies include only cause-dependent interventions, which are not able to reduce myocardial necrosis and optimize cardiac repair following infarction. This review highlights the cellular and molecular processes after myocardial injury and focuses on chemokines, the main modulators of the inflammatory and reparatory events, as the most valuable drug targets.

Overview of biologic response modifiers in infectious disease

The conventional treatment of infectious agents is increasingly encountering antimicrobial resistance. This resistance has led to an intense search for novel treatment modalities for infectious diseases. Elucidation of the mechanisms underlying the inhibitory activity of chemokines has been instrumental in the rational design of anti-human immunodeficiency virus chemokine drugs. The immune-based therapies, in combination with antimicrobial drugs, for viral hepatitis have attracted much attention. Recognition of toll-like receptors by synthetic immunomodulators is used for certain viral infections. New methodologies have the potential to identify novel targets and foster the development of individually tailored immunomodulatory drug treatments.

The interaction between different types of activated RAW 264.7 cells and macrophage inflammatory protein-1 alpha

Background

Two major ways of macrophage (MΦ) activation can occur in radiation-induced pulmonary injury (RPI): classical and alternative MΦ activation, which play important roles in the pathogenesis of RPI. MΦ can produce chemokine MΦ inflammatory protein-1α (MIP-1α), while MIP-1α can recruit MΦ. The difference in the chemotactic ability of MIP-1α toward distinct activated MΦ is unclear. We speculated that there has been important interaction of MIP-1α with different activated MΦ, which might contribute to the pathogenesis of RPI.

Methods

Classically and alternatively activated MΦ were produced by stimulating murine MΦ cell line RAW 264.7 cells with three different stimuli (LPS, IL-4 and IL-13); Then we used recombinant MIP-1α to attract two types of activated MΦ. In addition, we measured the ability of two types of activated MΦ to produce MIP-1α at the protein or mRNA level.

Results

Chemotactic ability of recombinant MIP-1α toward IL-13-treated MΦ was the strongest, was moderate for IL-4-treated MΦ, and was weakest for LPS-stimulated MΦ (p < 0.01). The ability of LPS-stimulated MΦ to secrete MIP-1α was significantly stronger than that of IL-4-treated or IL-13-treated MΦ (p < 0.01). The ability of LPS-stimulated MΦ to express MIP-1α mRNA also was stronger than that of IL-4- or IL-13-stimulated MΦ (p < 0.01).

Conclusions

The chemotactic ability of MIP-1α toward alternatively activated MΦ (M2) was significantly greater than that for classically activated MΦ (M1). Meanwhile, both at the mRNA and protein level, the capacity of M1 to produce MIP-1α is better than that of M2. Thus, chemokine MIP-1α may play an important role in modulating the transition from radiation pneumonitis to pulmonary fibrosis in vivo, through the different chemotactic affinity for M1 and M2.

Dose-response met-RANTES treatment of experimental periodontitis: a narrow edge between the disease severity attenuation and infection control

Chemokines and chemokine receptors have been implicated in the selective migration of leukocyte subsets to periodontal tissues, which consequently influences the disease outcome. Among these chemoattractants, the chemokines CCL3, CCL4 and CCL5 and its receptors, CCR1 and CCR5, have been associated with increased disease severity in mice and humans. Therefore, in this study we investigated the modulation of experimental periodontitis outcome by the treatment with a specific antagonist of CCR1 and 5 receptors, called met-RANTES. C57Bl/6 mice was orally infected with Aggregatibacter actinomycetemcomitans and treated with 0.05, 0.1, 0.5, 1.5 and 5 mg doses of met-RANTES on alternate days, and evaluated by morphometric, cellular, enzymatic and molecular methods. At 0.5 mg up to 5 mg doses, a strong reduction in the alveolar bone loss and inflammatory cell migration were observed. Interestingly, 5 mg dose treatment resulted in the maximum inhibition of inflammatory cell migration, but resulted in a similar inhibition of bone loss when compared with the lower doses, and also resulted in increased bacterial load and CRP response. When 0.5 and 5 mg therapy regimens were compared it was observed that both therapeutic protocols were able to downregulate the levels of pro-inflammatory, Th1-type and osteoclastogenic cytokines, and CD3+ and F4/80+ cells migration to periodontal tissues, but the high dose modulates host response in a more pronounced and unspecific and excessive way, interfering also with the production of antimicrobial mediators such as MPO, iNOS and IgG, and with GR1+ and CD19+ cells migration. Our results demonstrate a thin line between beneficial immunoregulation and impaired host defense during experimental periodontitis, and the determination of the exact equilibrium point is mandatory for the improvement of immune-targeted therapy of periodontitis.

C7 Anti-infective activity of immunomodulators

Infectious diseases continue to impact human morbidity and mortality. Every individual is vulnerable to microbial infections regardless of socioeconomic status, gender, age group or ethnic background. There has been an explosion of international air travel with an estimated 2 billion passengers travelling on commercial airlines every year. The rapid expansion of globalization and mass tourism has facilitated the spread of disease-causing pathogens from one continent to another at unprecedented rates.

Evidences of the cooperative role of the chemokines CCL3, CCL4 and CCL5 and its receptors CCR1+ and CCR5+ in RANKL+ cell migration throughout experimental periodontitis in mice

Periodontal disease (PD) is characterized by the inflammatory bone resorption in response to the bacterial challenge, in a host response that involves a series of chemokines supposed to control cell influx into periodontal tissues and determine disease outcome. In this study, we investigated the role of chemokines and its receptors in the immunoregulation of experimental PD in mice. Aggregatibacter actinomycetemcomitans-infected C57Bl/6 (WT) mice developed an intense inflammatory reaction and severe alveolar bone resorption, associated with a high expression of CCL3 and the migration of CCR5+, CCR1+ and RANKL+ cells to periodontal tissues. However, CCL3KO-infected mice developed a similar disease phenotype than WT strain, characterized by the similar expression of cytokines (TNF-alpha, IFN-gamma and IL-10), osteoclastogenic factors (RANKL and OPG) and MMPs (MMP-1, MMP-2, MMP-3, TIMP-1 and TIMP-3), and similar patterns of CCR1+, CCR5+ and RANKL+ cell migration. The apparent lack of function for CCL3 is possible due the relative redundancy of chemokine system, since chemokines such as CCL4 and CCL5, which share the receptors CCR1 and CCR5 with CCL3, present a similar kinetics of expression than CCL3. Accordingly, CCL4 and CCL5 kinetics of expression after experimental periodontal infection remain unaltered regardless the presence/absence of CCL3. Conversely, the individual absence of CCR1 and CCR5 resulted in a decrease of leukocyte infiltration and alveolar bone loss. When CCR1 and CCR5 were simultaneously inhibited by met-RANTES treatment a significantly more effective attenuation of periodontitis progression was verified, associated with lower values of bone loss and decreased counts of leukocytes in periodontal tissues. Our results suggest that the absence of CCL3 does not affect the development of experimental PD in mice, probably due to the presence of homologous chemokines CCL4 and CCL5 that overcome the absence of this chemokine. In addition, our data demonstrate that the absence of chemokine receptors CCR1+ and CCR5+ attenuate of inflammatory bone resorption. Finally, our data shows data the simultaneous blockade of CCR1 and CCR5 with MetRANTEs presents a more pronounced effect in the arrest of disease progression, demonstrating the cooperative role of such receptors in the inflammatory bone resorption process throughout experimental PD.

Sesamin inhibits bacterial formylpeptide-induced inflammatory responses in a murine air-pouch model and in THP-1 human monocytes

The reaction of human leukocytes to chemoattractants is an important component of the host immune response and also plays a crucial role in the development of inflammation. Sesamin has been shown to inhibit lipid peroxidation and regulate cytokine production. In this study, we examined the effect of sesamin on inflammatory responses elicited by the bacterial chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF) in vitro and in vivo and explored the mechanisms involved. fMLF is recognized by a human G protein-coupled receptor formyl peptide receptor (FPR) on phagocytic leukocytes. Sesamin at concentrations between 12.5 and 50 micromol/L inhibited fMLF-induced chemotaxis of human monocyte cell line THP-1 differentiated with dibutyryl cyclic AMP (P < 0.01). Similarly, sesamin inhibited FPR-transfected rat basophilic leukemia cell [epitope-tagged human FPR (ETFR) cell] migration toward fMLF (P < 0.01). In fMLF-induced inflammation in a murine air-pouch model, intraperitoneal administration of sesamin (12 mgkg(-1)d(-1) for 2 d) suppressed leukocyte infiltration into the air pouch induced by fMLF [(62.89 +/- 7.93) x 10(4) vs. (19.67 +/- 4.43) x 10(4) cells/air pouch; n = 9; P < 0.001]. Ca(2+) mobilization and mitogen-activated protein kinase extracellular signal-regulated kinase (ERK1/2) activation are involved in fMLF-induced leukocyte migration. Pretreatment of ETFR cells with sesamin inhibited fMLF-induced ERK1/2 phosphorylation in a dose-dependent manner but did not affect fMLF-induced Ca(2+) flux. Electrophoretic mobility shift assay showed that pretreatment of THP-1 cells with sesamin dose dependently inhibited fMLF-induced nuclear factor-kappaB (NF-kappaB) activation. These results suggest that sesamin inhibits leukocyte activation by fMLF through ERK1/2- and NF-kappaB-related signaling pathways and thus is a potential compound for the management of inflammatory diseases.

The green tea polyphenol (-)-epigallocatechin-3-gallate inhibits leukocyte activation by bacterial formylpeptide through the receptor FPR

Although green tea polyphenol catechin is considered as a potential anti-inflammatory agent, its effect on bacterial component-induced inflammation has been poorly investigated. We examined the capacity of epigallocatechin gallate (EGCG) to regulate leukocyte responses to bacterial chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (fMLF), which is recognized by a human G protein-coupled receptor FPR on phagocytic leukocytes. Pretreatment of human monocytic cells or FPR-transfected rat basophilic leukemia cells (ETFR cells) with EGCG significantly inhibited fMLF-induced chemotaxis. Intraperitoneal administration of EGCG in mice suppressed fMLF-induced leukocyte infiltration into the air pouch created in the skin. Mechanistic studies revealed that EGCG dose-dependently suppressed fMLF-induced calcium flux in monocytic cells and ETFR cells. fMLF-induced ETFR cell migration was significantly inhibited by a specific MEK1/2 inhibitor, PD98059, which was associated with reduction in fMLF-induced ERK1/2 phosphorylation. These results suggest that EGCG inhibits FPR-mediated leukocyte activation thus is a promising anti-inflammatory compound.

10 M-T7: measuring chemokine-modulating activity

Chemokines are important for activation of a host of cellular immune and inflammatory responses including cell signaling, activation, and communication. M-T7, a myxoma virus protein, inhibits the activity of chemokines by direct binding to chemokines and/or with glycosaminoglycans (GAGs). To study the effects of this chemokine-modulating protein (CMP), we use a variety of in vitro and in vivo techniques to evaluate M-T7 inhibition of inflammatory cells. To quickly analyze the effects of M-T7, changes in cell adhesion and membrane fluidity are measured as well as cell migration in mouse ascites. For more physiological analyses, an aortic transplant model in rodents is used to assess change in inflammatory cell infiltrates and vascular plaque growth (rejection). Utilization of the combination of these in vitro and in vivo techniques allows for a more complete study of the chemokine-modulating activity of M-T7, and can be used to study other immune and inflammation-modulating proteins.

The role of chemokines in controlling granulomatous inflammation in Schistosoma mansoni infection

Chemokines are a superfamily of low-molecular-weight cytokines that were initially described for their chemoattractant activity. It is now clear chemokines have several other activities that modulate immune processes. Chemokines appear to play a role in the pathogenesis of several inflammatory diseases. The role of chemokines and their receptors in mediating granulomatous inflammation induced by Schistosoma mansoni egg antigens presented in particulate manner have been studied in detail. Much less is known of the role of chemokines in mediating inflammation during the course of S. mansoni infection. Our studies in mice suggest a relevant role for the chemokine CCL3 and the receptor CCR5 in the pathogenesis of experimental S. mansoni infection. Absence of CCL3 is associated with decrease in granuloma size, fibrosis and parasite load. In humans, levels of CCL3 in plasma associate with disease severity and may be useful for diagnostic purposes. In contrast, absence of CCR5 is associated with enhanced lethality, granuloma size and fibrosis. It is suggested that the balance of chemokine production and chemokine receptor activation are important determinants of the fate of infection in experimental animals and humans.

The chemokine receptor Cxcr3 is not essential for acute cardiac allograft rejection in mice and rats

Chemokine receptors have gained attention as potential targets for novel therapeutic strategies. We investigated the mechanisms of allograft rejection in chemokine receptor Cxcr3-deficient mice using a model of acute heart allograft rejection in the strain combination BALB/c to C57BL/6. Allograft survival was minimally prolonged in Cxcr3-deficient mice compared to wild-type (wt) animals (8 vs. 7 days) and treatment with a subtherapeutic dose of cyclosporine A (CsA) led to similar survival in Cxcr3-deficient and wt recipients (13 vs. 12 days). At rejection grafts were histologically indistinguishable. Microarray analysis revealed that besides Cxcr3 only few genes were differentially expressed in grafts or in spleens from transplanted or untransplanted animals. Transcript analysis by quantitative RT-PCR of selected cytokines, chemokines, or chemokine receptors or serum levels of selected cytokines and chemokines showed similar levels between the two groups. Furthermore, in a rat heart allograft transplantation model treatment with a small molecule CXCR3 antagonist did not prolong survival despite full blockade of Cxcr3 in vivo. In summary, Cxcr3 deficiency or pharmacologic blockade does not diminish graft infiltration, tempo and severity of rejection. Thus, Cxcr3 does not appear to play a pivotal role in the allograft rejection models described here.

Manipulation of acute inflammatory lung disease

Inflammatory lung disease to innocuous antigens or infectious pathogens is a common occurrence and in some cases, life threatening. Often, the inflammatory infiltrate that accompanies these events contributes to pathology by deleterious effects on otherwise healthy tissue and by compromising lung function by consolidating (blocking) the airspaces. A fine balance, therefore, exists between a lung immune response and immune-mediated damage, and in some the "threshold of ignorance" may be set too low. In most cases, the contributing, potentially offending, cell population or immune pathway is known, as are factors that regulate them. Why then are targeted therapeutic strategies to manipulate them not more commonplace in clinical medicine? This review highlights immune homeostasis in the lung, how and why this is lost during acute lung infection, and strategies showing promise as future immune therapeutics.

CDIP-2, a synthetic peptide derived from chemokine (C-C motif) ligand 13 (CCL13), ameliorates allergic airway inflammation

Airway inflammation is characterized by selective recruitment of mononuclear and granulocytic cells. This recruitment is mediated by the action of chemotactic cytokines, such as chemokines. A number of chemokines and their receptors have been identified and proposed as potential therapeutic agents in allergic airway inflammation. One of these chemokines is chemokine (C-C motif) ligand 13 (CCL13), a CC chemokine that has been associated with allergic inflammatory diseases such as asthma and allergic rhinitis. To investigate alternative therapeutic agents to alleviate allergic inflammatory diseases, a number of chemokine-derived synthetic peptides were designed and tested for their ability to modulate in vitro and in vivo chemokine-mediated functions. Our results show that one of these peptides, CDIP-2, displayed antagonist functions in in vitro chemotaxis assays using monocytic cell lines. In addition, we found that CDIP-2 significantly reduced peribronchial, perivascular infiltrate and mucus overproduction in an ovalbumin-induced allergic lung inflammation murine model. Thus, CDIP-2 may be considered as part of a novel group of anti-inflammatory agents based on chemokine-derived synthetic peptides.

The role of chemokines in Schistosoma mansoni infection: insights from human disease and murine models

Chemokines are a superfamily of low-molecular-weight cytokines that were initially described for their chemoattractant activity. It is now clear chemokines have several other activities that modulate immune processes. More than 50 chemokines ligands and at least 19 receptors have been described to date. Depending on the number of N-terminal cysteine residues, chemokines are grouped in the subfamilies CXC, CC, C or CX3C. A growing body of evidence suggests a role for chemokines in the pathogenesis of several inflammatory diseases. Our studies involving mice and humans infected with Schistosoma mansoni suggest an important role of the chemokine CCL3 and its receptors (CCR1 and CCR5) in the pathogenesis of severe schistosomiasis. We suggest that the differential activation of CCR1 or CCR5 during the course of schistosomiasis may dictate the outcome of the disease.

The pattern of immune cell infiltration in chromoblastomycosis: involvement of macrophage inflammatory protein-1 alpha/CCL3 and fungi persistence

Chromoblastomycosis (CR) is a subcutaneous chronic mycosis characterized by a granulomatous inflammatory response. However, little is known regarding the pattern of leukocyte subsets in CR and the pathways involved in their recruitment. The objective of this study was to assess the cellular subsets, chemokine, chemokine receptors and enzymes in CR. The inflammatory infiltrate was characterized by immunohistochemistry using antibodies against macrophages (CD68), Langerhans'cells (S100), lymphocytes (CD3, CD4, CD8, CD45RO, CD20 and CD56) and neutrophils (CD15). The expression of MIP-1alpha (Macrophage inflammatory protein-1alpha), chemokine receptors (CXCR3 and CCR1) and enzymes (superoxide dismutase-SOD and nitric oxide synthase-iNOS) was also evaluated by the same method. We observed an increase in all populations evaluated when compared with the controls. Numbers of CD15(+) and CD56(+) were significantly lower than CD3(+), CD4(+), CD20(+) and CD68(+) cells. Statistical analysis revealed an association of fungi numbers with CD3, CD45RO and iNOS-positive cells. Furthermore, MIP-1alpha expression was associated with CD45RO, CD68, iNOS and CXCR3. Our results suggest a possible role of MIP-1alpha and fungi persistence in the cell infiltration in CR sites.

Chemokine: receptor structure, interactions, and antagonism

Chemokines are critical mediators of cell migration during routine immune surveillance, inflammation, and development. Chemokines bind to G protein-coupled receptors and cause conformational changes that trigger intracellular signaling pathways involved in cell movement and activation. Although chemokines evolved to benefit the host, inappropriate regulation or utilization of these proteins can contribute to or cause many diseases. Specific chemokine receptors provide the portals for HIV to get into cells, and others contribute to inflammatory diseases and cancer. Thus, there is significant interest in developing receptor antagonists. To this end, the structures of ligands coupled with mutagenesis studies have revealed mechanisms for antagonism based on modified proteins. Although little direct structural information is available on the receptors, binding of small molecules to mutant receptors has allowed the identification of key residues involved in the receptor-binding pockets. In this review, we discuss the current knowledge of chemokine:receptor structure and function, and its contribution to drug discovery.

Physiological immunity or pathological autoimmunity--a question of balance

Chemokines (CKs) are chemo-attractants that mobilize and activate leukocytes of the immune system. CKs and their receptors have become targets for drug discovery and development on the basis of correlations between their expression profiles and autoimmune diseases. Essential for both physiological immunity and pathological autoimmunity, these immune messengers and regulators have proven to be tantalizing drug targets. Drug inhibitors of disease-related CK receptors adversely affect physiological processes which are unrelated to the targeted disease. We argue that drugs which modulate, rather than negate CK activity, may be the answer to fortuitous and deleterious side effects. CKs, more than their receptors, lend themselves to therapeutic modulation that is disease specific.

Enhanced recruitment of CX3CR1+ T cells by mucosal endothelial cell-derived fractalkine in inflammatory bowel disease

BACKGROUND & AIMS

Fractalkine (FKN/CX3CL1) is a unique chemokine combining adhesive and chemotactic properties. We investigated FKN production by the mucosal microvasculature in inflammatory bowel disease (IBD), its capacity for leukocyte recruitment into the gut, and the number of CX3CR1+ cells in the circulation and mucosa of IBD patients.

METHODS

The expression of FKN by human intestinal microvascular endothelial cells (HIMECs) and CX3CR1 by circulating cells was evaluated by flow cytometry, and mucosal CX3CR1+ cells were enumerated by immunohistochemistry. The capacity of FKN to mediate leukocyte binding to HIMECs was assessed by immunoblockade, and to induce HIMEC transmigration by a Transwell system.

RESULTS

The spontaneously low HIMEC FKN expression was enhanced markedly by tumor necrosis factor-alpha plus interferon-gamma stimulation, or direct leukocyte contact. This effect was significantly stronger in IBD than control HIMECs. Up-regulation of HIMEC FKN expression was dependent on p38 and extracellular signal-regulated kinase phosphorylation, as was abrogated by selective mitogen-activated protein kinase inhibitors. Circulating T cells contained significantly higher numbers of CX3CR1+ cells in active IBD than inactive IBD or healthy subjects, and IBD mucosa contained significantly more CX3CR1+ cells than control mucosa. Antibody-blocking experiments showed that FKN was a major contributor to T- and monocytic-cell adhesion to HIMECs. Finally, FKN enhanced the expression of active beta1 integrin on leukocytes and mediated leukocyte HIMEC transmigration.

CONCLUSIONS

In view of the capacity of FKN to mediate leukocyte adhesion, chemoattraction, and transmigration, its increased production by mucosal microvascular cells and increased numbers of circulating and mucosal CX3CR1+ cells in IBD point to a significant role of FKN in disease pathogenesis.

PI3Kgamma inhibition: towards an 'aspirin of the 21st century'?

Class IB phosphatidylinositol 3-kinase p110gamma (PI3Kgamma) has gained increasing attention as a promising drug target for the treatment of inflammatory disease. Extensive target-validation data are available, which are derived from studies using both pharmacological and genetic tools. More recent findings have uncovered further therapeutic applications for PI3Kgamma inhibitors, opening up potentially huge opportunities for these drugs. Several companies have been pursuing small-molecule PI3Kgamma inhibitor projects, but none of them has progressed to the clinic yet. Here, we discuss the insights gained so far and the main challenges that are emerging on the path to developing PI3Kgamma inhibitors for the treatment of human disease.

In vitro selection of RNA aptamers that block CCL1 chemokine function

CCL1, the CCR8 ligand, is a CC chemokine secreted by activated monocytes and lymphocytes and is a potent chemoattractant for these cell types. The in vivo role of the CCL1/CCR8 axis in Th2-mediated inflammation is far from clear. Ligand neutralisation studies reported discrepancies in the effect of CCL1/CCR8 and CCR8 knockout studies showed very different insights into the functional role of the CCR8. To further study the biological function of CCL1, we focused on the generation and characterisation of RNA aptamers. We report here the in vitro isolation of the first nuclease resistant and selective RNA aptamer (T48) with high-binding affinity for human and mouse CCL1. The T48 aptamer but not a random control aptamer antagonises CCL1 function in a dose-dependent fashion in both heparin binding and chemotaxis assays. To our knowledge, the T48 aptamer constitutes one of the most potent CCL1 antagonists reported to date and is an excellent tool to dissect CCL1-specific function in vivo. The T48 aptamer may also have potential as new generation of therapeutic tools.

Potential inhibitors of chemokine function: analysis of noncovalent complexes of CC chemokine and small polyanionic molecules by ESI FT-ICR mass spectrometry

Chemokines play a critical role in inducing chemotaxis, extravasation, and activation of leukocytes both in routine immunosurveillance and autoimmune diseases. Traditionally, to disrupt chemokine function, strategies have focused on blockage of its interaction with the receptor. Recently, it has been demonstrated that binding to glycosaminoglycans (GAGs) is also required for the in vivo activity of many chemokines. Thus, interference with the GAG-binding of chemokines may offer an alternative, valid, anti-inflammatory strategy. However, the potential of using small polyanions to inhibit the interactions between chemokines and cell surface GAGs has not been fully explored. In this study, a mass spectrometry based filtration trapping assay was utilized to study the interactions between two CCR 2 ligands (MCP-1/CCL2 and MCP-3/CCL7) and a series of low molecular weight, polyanionic molecules. Findings were confirmed by using a hydrophobic trapping assay. The results indicated that Arixtra (fondaparinux sodium), sucrose octasulfate, and suramin were specific binders of the chemokines, while cyclodextrin sulfate, although the most highly sulfated molecule among the ones investigated, showed no binding. The binding stoichiometry of the small molecule ligand was determined from the measured molecular weight of the noncovalent complex. Furthermore, the dissociation constant between MCP-3 and Arixtra was determined by using electrospray ionization Fourier transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry, which compared favorably with the result of the isothermal titration calorimetry (ITC) assay. The relative binding affinity of these ligands to MCP-3 was also determined using a competitive filtration trapping assay.

Schistosoma mansoni secretes a chemokine binding protein with antiinflammatory activity

The coevolution of humans and infectious agents has exerted selective pressure on the immune system to control potentially lethal infections. Correspondingly, pathogens have evolved with various strategies to modulate and circumvent the host's innate and adaptive immune response. Schistosoma species are helminth parasites with genes that have been selected to modulate the host to tolerate chronic worm infections, often for decades, without overt morbidity. The modulation of immunity by schistosomes has been shown to prevent a range of immune-mediated diseases, including allergies and autoimmunity. Individual immune-modulating schistosome molecules have, therefore, therapeutic potential as selective manipulators of the immune system to prevent unrelated diseases. Here we show that S. mansoni eggs secrete a protein into host tissues that binds certain chemokines and inhibits their interaction with host chemokine receptors and their biological activity. The purified recombinant S. mansoni chemokine binding protein (smCKBP) suppressed inflammation in several disease models. smCKBP is unrelated to host proteins and is the first described chemokine binding protein encoded by a pathogenic human parasite and may have potential as an antiinflammatory agent.

The therapeutic potential in targeting CCR5 and CXCR4 receptors in infectious and allergic pulmonary disease

Targeting chemokines and chemokine receptors in various acute and chronic pulmonary diseases remains a vibrant area of basic and clinical research despite major hurdles including cross-species barriers, toxicity, and redundancy. In this review, we draw upon our basic research with a murine model in which innate and acquired immunity are linked in the development and maintenance of chronic asthma due to Aspergillus fumigatus. Using intact and genetically altered mice, studies have also been undertaken to elucidate safe and effective therapeutic strategies that interrupt the initiation and amplification of inflammatory and immune events that follow the intrapulmonary introduction of Aspergillus into A. fumigatus-sensitized mice. These events include resident immune cell activation, immune and inflammatory cell recruitment to the airways, changes in lung physiology, and profound changes in the architecture of the airway due to the activation of lung resident cells. The expression of 2 major chemokine receptors, namely, CC chemokine receptor (CCR) 5 and CXC chemokine receptor (CXCR) 4, has been identified and their roles in innate and acquired immune events during fungal asthma have been explored. CCR5 and CXCR4 are best known for their roles in human immunodeficiency virus-1 (HIV-1) infection, but both are attractive targets in the context of overt inflammatory and remodeling responses in the lung. This avenue of research is markedly enhanced by the existence of numerous small molecule antagonists that are available to selectively target these receptors.

Modulating CCR2 and CCL2 at the blood-brain barrier: relevance for multiple sclerosis pathogenesis

Chemokines and chemokine receptors play a key role in the transmigration of leucocytes across the blood-brain barrier (BBB). CCR2 is the major receptor for CCL2, a potent monocyte and T cell chemoattractant. CCR2 and CCL2 have been consistently associated with a pathogenic role in experimental autoimmune encephalomyelitis, using knockout and transgenic mice, neutralizing antibodies, peptide antagonists and DNA vaccination. However, the significance of CCL2 and CCR2 in multiple sclerosis is enigmatic, because CCL2 levels are consistently decreased in the CSF of patients with this disease and other chronic neuroinflammatory conditions, despite abundant expression within lesional multiple sclerosis tissues. This study used an in vitro BBB model to test the hypothesis that CCL2 is removed from the extracellular fluid by CCR2-positive migrating cells as they cross the BBB, resulting in decreased CSF CCL2 levels. We showed that CCR2-positive T cells and monocytes migrated selectively across the in vitro BBB, and that CCL2 on the abluminal (tissue) side was consumed by migrating T cells and monocytes. Next, we used a new anti-CCR2 antibody to show that CCR2-positive mononuclear inflammatory cells could be readily detected in appropriate positive control tissues, but that CCR2+ cells were very infrequently found in multiple sclerosis lesions. We then showed that CCR2 receptor density on T cells and monocytes was specifically downregulated upon in vitro BBB transmigration in response to CCL2, but not irrelevant chemokines. These findings document a novel strategy for analysing chemokine receptor function in inflammatory CNS disease, and support the hypothesis that CCL2 is consumed by migrating inflammatory cells, which downregulate CCR2, as they cross the BBB.

Differential expression of chemokines and chemokine receptors in inflammatory periapical diseases

BACKGROUND

Periapical lesions are thought to be the result of a local inflammatory response mediated by inflammatory cell infiltration and production of inflammatory mediators. Although chemokines are strongly implicated in the migration and activation of leukocytes in different inflammatory diseases and experimental models, little is known regarding the expression of chemokines and their receptors in human apical periodontitis.

OBJECTIVE AND METHODS

The objective of this study was to determine the expression of chemokines and their receptors by real-time polymerase chain reaction in samples obtained from healthy gingiva, periapical granulomas, and inflammatory periradicular cysts. The inflammatory infiltrate was characterized by immunohistochemistry.

RESULTS

Comparing cysts and granulomas, an increase in CD4+ and CD8+ cells was observed in granulomas, despite the similar numbers of CD45RO-positive cells detected in both lesions. The analysis of mRNA expression revealed increased levels of CCR1, CCR2, CCR3, CCR5, CXCR1, and CXCR3 in both types of lesion compared with controls. Cysts exhibited a higher expression of CCR3, CCR5, CXCR1, and CXCR3 compared to granulomas. A significantly higher expression of RANTES, IP-10, and MCP-1 was detected in cysts compared with controls or granulomas. The expression of interleukin-8, MIP-1alpha, and MIP-1beta was not different in the three experimental groups.

CONCLUSIONS

The increase in Th1 type (CCR1, CCR5, and CXCR3) and Th2 type (CCR2 and CCR3) receptors in both periapical lesions suggests the concomitant occurrence of Th1 and Th2 responses. Furthermore, the prevalent expression of the receptors CCR3, CCR5, CXCR1, and CXCR3 and of the chemokines RANTES, IP-10, and MCP-1 in cysts may point to a role in the progression of granulomas to cysts.

Identification of potent and selective RNA antagonists of the IFN-gamma-inducible CXCL10 chemokine

CXCL10 (also known as IP-10 in humans and CRG-2 in mice) is a nonglycosylated chemokine and a member of the non-ELR CXC chemokine subfamily implicated in a variety of inflammatory conditions. The role of CXCL10 in different disease states still requires clarification, and new approaches are necessary to better understand its biological function. We report here the isolation of a series of nuclease-resistant RNA aptamers that act to antagonize human CXCL10 function in a number of in vitro and cell-based assays. The two most potent aptamers identified were highly selective for human CXCL10. A further aptamer was identified that antagonized both the human and the mouse CXCL10. A combination of a molecular-biology-based truncation and solid-phase synthesis enabled the truncation of one of the aptamers from 71 to 34 nucleotides. This was followed by PEGylation, 3' capping, and further stabilization of the RNA aptamer, while its high potency was maintained. These aptamers could be utilized as powerful target validation tools and may also have therapeutic potential. To our knowledge, the CXCL10 aptamers generated are the most potent antagonists of CXCL10/CXCR3 signaling reported to date.

Therapeutic targeting of CCR1 attenuates established chronic fungal asthma in mice

CC chemokine receptor 1 (CCR1) represents a promising target in chronic airway inflammation and remodeling due to fungus-associated allergic asthma. The present study addressed the therapeutic effect of a nonpeptide CCR1 antagonist, BX-471, in a model of chronic fungal asthma induced by Aspergillus fumigatus conidia. BX-471 treatment of isolated macrophages inhibited CCL22 and TNF-alpha and promoted IL-10 release. BX-471 also increased toll like receptor-9 (TLR9) and decreased TLR2 and TLR6 expression in these cells. When administered daily by intraperitoneal injection, from days 15 to 30 after the initiation of chronic fungal asthma, BX-471 (3, 10, or 30 mg kg(-1)) dose-dependently reduced airway inflammation, hyper-responsiveness, and remodeling at day 30 after conidia challenge. The maximal therapeutic effect was observed at the 10 mg kg(-1) dose. In summary, the therapeutic administration of BX-471 significantly attenuated experimental fungal asthma via its effects on both innate and adaptive immune processes.

Chemokine-glycosaminoglycan binding: specificity for CCR2 ligand binding to highly sulfated oligosaccharides using FTICR mass spectrometry

Glycosaminoglycans (GAGs) have recently been demonstrated to be required for the in vivo activity of several chemokines. Minimally, the interaction is thought to provide a mechanism for retention at the site of secretion and the formation of chemokine gradients that provide directional cues for receptor bearing cells, particularly in the presence of shear forces. Thus, a key issue will be to determine the sequence and structure of the GAGs that bind to specific chemokines. Herein, we describe a mass spectrometry assay that was developed to detect protein-oligosaccharide noncovalent complexes, in this case chemokine-GAG interactions, and to select for high affinity GAGs. The process is facilitated by the ability of electrospray ionization to transfer the intact noncovalent complexes from solution into the gas phase. The elemental composition as well as the binding stoichiometry can be calculated from the mass of the complex. Ligands of the chemokine receptor, CCR2 (MCP-1/CCL2, MCP-2/CCL8, MCP-3/CCL7, MCP-4/CCL13, and Eotaxin/CCL11), and the CCR10 ligand CTACK/CCL27 were screened against a small, highly sulfated, heparin oligosaccharide library with limited structural variation. The results revealed heparin octasaccharides with 11 and 12 sulfates as binders. Oligomerization of some chemokines was observed upon GAG binding, whereas in other instances only the monomeric noncovalent complex was identified. The results indicate that, in contrast to the apparent redundancy in the chemokine system, where several chemokines bind and activate the same receptor, these chemokines could be differentiated into two groups based on the stoichiometry of their complexes with the heparin oligosaccharides.

Treatment of ovalbumin-induced experimental allergic bronchitis in rats by inhaled inhibitor of secretory phospholipase A(2)

BACKGROUND

The pathophysiology of asthma involves the action of inflammatory/allergic lipid mediators formed following membrane phospholipid hydrolysis by phospholipase A(2) (PLA(2)). Cysteinyl leukotrienes are considered potent inducers of bronchoconstriction and airway remodelling. Ovalbumin (OVA) induced bronchoconstriction in rats is associated with increased secretory PLA(2) (sPLA(2)) activation and cysteinyl leukotriene production, together with suppression of cytosolic PLA(2) and prostaglandin E(2). These processes are reversed when the animals are pretreated systemically with an extracellular cell impermeable sPLA(2) inhibitor which also suppresses the early allergic reaction to OVA challenge. In this study we examine the capacity of the sPLA(2) inhibitor to ameliorate inflammatory and allergic manifestations (early and late bronchoconstriction) of OVA induced allergic bronchitis in rats when the inhibitor was administered by inhalation to confine it to the airways.

METHODS

Rats sensitised with OVA were treated with the sPLA(2) inhibitor hyaluronic acid-linked phosphatidyl ethanolamine (HyPE). The rats were divided into four groups (n = 10 per group): (1) naïve controls (no sensitisation/no treatment); (2) positive controls (sensitisation + challenge with OVA inhalation and subcutaneous injection of 1 ml saline before each challenge; (3) sensitisation + challenge with OVA and HyPE inhalation before every challenge; and (4) sensitisation + challenge with OVA and treatment with subcutaneous dexamethasone (300 mug) before each challenge as a conventional reference. Another group received no treatment with HyPE during the sensitisation process but only before or after challenge of already sensitised rats. Pulmonary function was assessed and changes in the histology of the airways, levels of cysteinyl leukotrienes in BAL fluid, and the production of nitric oxide (No) and tumour necrosis factor alpha (TNFalpha) by BAL macrophages were determined.

RESULTS

Inhalation of HyPE markedly suppressed OVA induced early and late asthmatic reactions as expressed by bronchoconstriction, airway remodelling (histology), cysteinyl leukotriene level in BAL fluid, and production of TNFalpha and NO by BAL macrophages. OVA induced bronchoconstriction in sensitised non-pretreated rats was also inhibited by inhalation of HyPE either before or after the challenge.

CONCLUSIONS

These findings confirm the pivotal role of sPLA(2) in the pathophysiology of both the immediate allergic response and the inflammatory asthmatic process. Control of airway sPLA(2) may be a new therapeutic approach to the treatment of asthma.

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.