The coordinated action of CC chemokines in the lung orchestrates allergic inflammation and airway hyperresponsiveness

Chemokine receptors: understanding their role in asthmatic disease

The incidence, prevalence, and severity of asthma have been increasing steadily in recent years. Prophylactic treatment of this disease and of episodic asthmatic flares is aimed at preventing excessive inflammation in lung tissue and airways. Because chemokines and chemokine receptors are critical mediators of leukocyte trafficking and recruitment, there is the potential to pharmaceutically target these proteins to regulate inflammation. Asthma-associated inflammation is characterized by the infiltration of eosinophils and T helper type 2 cells. Early studies investigated the role of chemokine receptors, which have been shown to predominate on these cell populations.

Chemokine receptor antagonists: a novel therapeutic approach in allergic diseases

The aim of this review is to give an overview of the role of chemokines, particularly ligands of the CC chemokine receptor CCR3, in allergic diseases and to show the new concept in the treatment of allergies using chemokine receptor antagonists. Allergic diseases such as allergic asthma, allergic rhinitis and atopic dermatitis are characterized by a complex interaction of different cell types and mediators. Among this, Th2 cells, mast cells, basophils and eosinophils are found in the inflamed tissue due to the attraction of chemokines. Of all the known chemokine receptors, the chemokine receptor CCR3 seems to play the major role in allergic diseases which is supported by the detection of this receptor on the cell types mentioned above. Therefore, academic and industrial research focus on compounds to block this receptor. To date, certain chemokine receptor antagonists derived from peptides and small molecules exist to block the chemokine receptor CCR3. However, the in vivo data about these compounds and the mechanisms of receptor interaction are poorly understood, as yet. For the development of additional chemokine receptor antagonists, more details about the interaction between the ligands and their receptors are required. Therefore, additional studies will lead to the identification of novel CCR3 chemokine receptor antagonists, which can be therapeutically used in allergic asthma, allergic rhinitis, and atopic dermatitis.

Eosinophil function in allergic inflammation: from bone marrow to tissue response

The role of the eosinophil in the pathophysiology of allergy and asthma has been the focus of intense interest during the past two decades. Although the presence of eosinophils in humans with allergy and asthma is well established, the precise role of this cell in human and animal tissue response is still unclear. However, recent developments in research on many organ systems have provided novel insights into the possible underlying role of the eosinophil in both allergic and nonallergic inflammation. In this review, we examine the pathways associated with eosinophil recruitment and activation, and discuss these findings with reference to clinically defined categories.

Interference with Heparin Binding and Oligomerization Creates a Novel Anti-Inflammatory Strategy Targeting the Chemokine System

A hallmark of autoimmunity and other chronic diseases is the overexpression of chemokines resulting in a detrimental local accumulation of proinflammatory immune cells. Chemokines play a pivotal role in cellular recruitment through interactions with both cell surface receptors and glycosaminoglycans (GAGs). Anti-inflammatory strategies aimed at neutralizing the chemokine system have to-date targeted inhibition of the receptor-ligand interaction with receptor antagonists. In this study, we describe a novel strategy to modulate the inflammatory process in vivo through mutation of the essential heparin-binding site of a proinflammatory chemokine, which abrogates the ability of the protein to form higher-order oligomers, but retains receptor activation. Using well-established protocols to induce inflammatory cell recruitment into the peritoneal cavity, bronchoalveolar air spaces, and CNS in mice, this non-GAG binding variant of RANTES/CCL5 designated [44AANA47]-RANTES demonstrated potent inhibitory capacity. Through a combination of techniques in vitro and in vivo, [44AANA47]-RANTES appears to act as a dominant-negative inhibitor for endogenous RANTES, thereby impairing cellular recruitment, not through a mechanism of desensitization. [44AANA47]-RANTES is unable to form higher-order oligomers (necessary for the biological activity of RANTES in vivo) and importantly forms nonfunctional heterodimers with the parent chemokine, RANTES. Therefore, although retaining receptor-binding capacity, altering the GAG-associated interactive site of a proinflammatory chemokine renders it a dominant-negative inhibitor, suggesting a powerful novel approach to generate disease-modifying anti-inflammatory reagents.

Dendritic cell-mediated T cell polarization

Effective defense against diverse types of micro-organisms that invade our body requires specialized classes of antigen-specific immune responses initiated and maintained by distinct subsets of effector CD4(+) T helper (Th) cells. Excessive or detrimental (e.g., autoimmune) responses by effector T cells are controlled by regulatory T cells. The optimal balance in the development of the different types of effector and regulatory Th cells is orchestrated by dendritic cells (DC). This review discusses the way DC adapt the T cell response to the type of pathogen, focusing on the tools that DC use in this management of the T cell response.

Dysregulated inflammatory response to Candida albicans in a C5-deficient mouse strain

Experimental infection of inbred mouse strains with Candida albicans provides a good model system to identify host genetic determinants that regulate onset of, response to, and ultimate outcome of disseminated candidiasis. The A/J mouse strain is exquisitely sensitive to infection with C. albicans, while the C57BL/6J strain is relatively resistant, as measured by survival following intravenous injection of Candida blastospores. This differential susceptibility is caused by an A/J-specific loss-of-function mutation in the C5 component of the complement pathway. C5 plays several critical roles in host response to infection, including target lysis and phagocyte recruitment. Therefore, to determine which of its functions were required for host resistance to candidiasis, a detailed comparative analysis of pathophysiology and host response to acute C. albicans infection was conducted in A/J and C57BL/6J mice. C5-sufficient C57BL/6J mice were found to succumb late in infection due to severe kidney pathology, typified by fungal replication and robust neutrophil-based inflammatory response associated with extensive tissue damage. In contrast, A/J mice were moribund within 24 h postinfection but displayed little if any kidney damage despite an inability to mobilize granulocytes and a high fungal load in the kidney. Rather, C5 deficiency in A/J mice was associated with higher levels of circulating cytokines tumor necrosis factor alpha, interleukin-6, monocyte chemotactic protein 1 (MCP-1), MCP-5, and eotaxin in response to C. albicans. Transfer of the C5-defective allele from A/J onto a C57BL/6J genetic background in recombinant congenic strain BcA17 recapitulated the phenotypic aspects of the susceptibility of A/J mice to C. albicans, confirming the causative role of C5 deficiency in the dysregulated cytokine response.

Impact of cethromycin (ABT-773) therapy on microbiological, histologic, immunologic, and respiratory indices in a murine model of Mycoplasma pneumoniae lower respiratory infection

Mycoplasma pneumoniae is a major etiologic agent of acute lower respiratory infections. We evaluated the antimicrobial and immunologic effects of cethromycin (ABT-773), a ketolide antibiotic, for the treatment of M. pneumoniae pneumonia in a mouse model. Eight-week-old BALB/c mice were inoculated intranasally once with 10(6) CFU of M. pneumoniae on day 0. Treatment was started 24 h after inoculation. Groups of mice were treated subcutaneously with cethromycin at 25 mg/kg of body weight or with placebo daily until sacrifice. Five to ten mice per group were evaluated at days 1, 4, 7, and 10 after inoculation. Outcome variables included bronchoalveolar lavage (BAL) for M. pneumoniae quantitative culture and cytokine and chemokine concentration determinations by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], interleukin-1beta [IL-1beta], IL-2, IL-4, IL-12, granulocyte-macrophage colony-stimulating factor, IL-8, monocyte chemoattractant protein 1 [MCP-1], and macrophage inflammatory protein 1alpha [MIP-1alpha]), histopathologic score of the lungs (HPS), and pulmonary function tests (PFT) using whole-body, unrestrained plethysmography at the baseline and post-methacholine exposure as indicators of airway obstruction (AO) and airway hyperresponsiveness (AHR), respectively. The cethromycin-treated mice had a greater reduction in M. pneumoniae culture titers than placebo-treated mice, reaching statistical significance on days 7 and 10 (P < 0.05). HPS was significantly reduced in cethromycin-treated mice compared with placebo-treated mice on days 4, 7, and 10 (P < 0.05). Cytokine concentrations in BAL samples were reduced in mice that received cethromycin, and the differences were statistically significant for 7 of the 10 cytokines measured (TNF-alpha, IFN-gamma, IL-1beta, IL-8, IL-12, MCP-1, and MIP-1alpha) on day 4 (P < 0.05). PFT values were improved in the cethromycin-treated mice, with AO and AHR significantly reduced on day 4 (P < 0.05). In this mouse model, treatment with cethromycin significantly reduced M. pneumoniae culture titers in BAL samples, cytokine and chemokine concentrations in BAL samples, histologic inflammation in the lungs, and disease severity as defined by AO and AHR.

n-Nonanoyl-CC chemokine ligand 14, a potent CC chemokine ligand 14 analogue that prevents the recruitment of eosinophils in allergic airway inflammation

CCR3 is responsible for tissue infiltration of eosinophils, basophils, mast cells, and Th2 cells, particularly in allergic diseases. In this context, CCR3 has emerged as a target for the treatment of allergic asthma. It is well known that the N-terminal domain of chemokines is crucial for receptor binding and, in particular, its activation. Based on this background, we investigated a number of N-terminally truncated or modified peptides derived from the chemokine CCL14/hemofiltrate CC chemokine-1 for their ability to modulate the activity of CCR3. Among 10 derivatives tested, n-nonanoyl (NNY)-CCL14[10-74] (NNY-CCL14) was the most potent at evoking the release of reactive oxygen species and inducing chemotaxis of human eosinophils. In contrast, NNY-CCL14 has inactivating properties on human eosinophils, because it is able to induce internalization of CCR3 and to desensitize CCR3-mediated intracellular calcium release and chemotaxis. In contrast to naturally occurring CCL11, NNY-CCL14 is resistant to degradation by CD26/dipeptidyl peptidase IV. Because inhibition of chemokine receptors through internalization is a reasonable therapeutic strategy being pursued for HIV infection, we tested a potential inhibitory effect of NNY-CCL14 in two murine models of allergic airway inflammation. In both OVA- and Aspergillus fumigatus-sensitized mice, i.v. treatment with NNY-CCL14 resulted in a significant reduction of eosinophils in the airways. Moreover, airway hyper-responsiveness was shown to be reduced by NNY-CCL14 in the OVA model. It therefore appears that an i.v. administered agonist internalizing and thereby inhibiting CCR3, such as NNY-CCL14, has the potential to alleviate CCR3-mediated diseases.

Aspergillus antigen induces robust Th2 cytokine production, inflammation, airway hyperreactivity and fibrosis in the absence of MCP-1 or CCR2

BACKGROUND

Asthma is characterized by type 2 T-helper cell (Th2) inflammation, goblet cell hyperplasia, airway hyperreactivity, and airway fibrosis. Monocyte chemoattractant protein-1 (MCP-1 or CCL2) and its receptor, CCR2, have been shown to play important roles in the development of Th2 inflammation. CCR2-deficient mice have been found to have altered inflammatory and physiologic responses in some models of experimental allergic asthma, but the role of CCR2 in contributing to inflammation and airway hyperreactivity appears to vary considerably between models. Furthermore, MCP-1-deficient mice have not previously been studied in models of experimental allergic asthma.

METHODS

To test whether MCP-1 and CCR2 are each required for the development of experimental allergic asthma, we applied an Aspergillus antigen-induced model of Th2 cytokine-driven allergic asthma associated with airway fibrosis to mice deficient in either MCP-1 or CCR2. Previous studies with live Aspergillus conidia instilled into the lung revealed that MCP-1 and CCR2 play a role in anti-fungal responses; in contrast, we used a non-viable Aspergillus antigen preparation known to induce a robust eosinophilic inflammatory response.

RESULTS

We found that wild-type C57BL/6 mice developed eosinophilic airway inflammation, goblet cell hyperplasia, airway hyperreactivity, elevations in serum IgE, and airway fibrosis in response to airway challenge with Aspergillus antigen. Surprisingly, mice deficient in either MCP-1 or CCR2 had responses to Aspergillus antigen similar to those seen in wild-type mice, including production of Th2 cytokines.

CONCLUSION

We conclude that robust Th2-mediated lung pathology can occur even in the complete absence of MCP-1 or CCR2.

Requirement for CD28 in the effector phase of allergic airway inflammation

Central to the pathogenesis of allergic airway inflammation are the activation and differentiation of T lymphocytes. This process requires the participation of the CD28 costimulatory receptor. Blockade of CD28 has been demonstrated to prevent inflammation and airway hyperreactivity in a murine model of asthma. Whether this is due specifically to defects in initial T cell activation or whether effector responses are also impaired has not been determined. Using adoptive transfer studies of Ag-specific lymphocytes, we demonstrate that CD28 has a critical role in both the induction and effector phase of allergic airway inflammation. Transfer of in vitro activated and Th2-differentiated Ag-specific lymphocytes from wild-type hosts restored inflammation, but not tissue eosinophilia in CD28-deficient recipients. Furthermore, similarly activated and differentiated CD28-deficient lymphocytes were ineffective at mediating inflammation in wild-type recipients. Secondary cytokine and proliferative responses of activated Th2 cells were highly dependent on CD28 in vitro. Moreover, eosinophil recruitment to both the lung and peritoneum is impaired by the lack of CD28, suggesting a generalized defect in the ability of eosinophils to accumulate at sites of inflammation in vivo. These data identify a novel role for CD28 in the effector phase of allergic airway inflammation and suggest that inhibition of this pathway may be a useful therapeutic intervention in previously sensitized individuals.

Eosinophils and atopic dermatitis

In spite of the progress regarding the description of immunological phenomena associated with atopic dermatitis (AD), the pathogenesis of this disease still remains unclear. The presence of eosinophils in the inflammatory infiltrate of AD has long been established. Eosinophil numbers as well as eosinophil granule protein levels in peripheral blood are elevated in most AD patients and appear to correlate with disease activity. Moreover, eosinophil granule proteins, which possess cytotoxic activity, are deposited in the skin lesions. These observations indicate a role of eosinophils in the pathogenesis of AD. Furthermore, AD is associated with increased production of T helper 2 cytokines including interleukin (IL)-5, which specifically acts on eosinophils, resulting in accelerated eosinophilopoiesis, chemotaxis, cell activation, and delayed apoptosis. Therefore, IL-5 is an interesting target for experimental therapy in this inflammatory disorder of the skin. Such studies might result in new insights into the pathogenetic role of eosinophils in AD.

The C10/CCL6 chemokine and CCR1 play critical roles in the pathogenesis of IL-13-induced inflammation and remodeling

IL-13 is a potent stimulator of inflammation and tissue remodeling that plays a key role in the pathogenesis of a wide variety of human disorders. To further understand these responses, studies were undertaken to define the role(s) of the chemokine C10/CCL6 in the pathogenesis of IL-13-induced alterations in the murine lung. IL-13 was a very potent stimulator of C10/CCL6 mRNA and protein, and IL-13-induced inflammation, alveolar remodeling, and compliance alterations were markedly ameliorated after C10/CCL6 neutralization. Treatment with anti-C10/CCL6 decreased the levels of mRNA encoding matrix metalloproteinase-2 (MMP-2), MMP-9, and tissue inhibitor of metalloproteinase-4 (TIMP-4) in lungs from wild-type mice. C10/CCL6 neutralization also decreased the ability of IL-13 to stimulate the production of monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, MMP-2, MMP-9, and cathepsins-K, -L, and -S and the ability of IL-13 to inhibit alpha1-antitrypsin. In accord with these findings, a targeted null mutation of CCR1, a putative C10/CCL6 receptor, also decreased IL-13-induced inflammation and alveolar remodeling and caused alterations in chemokines, proteases, and antiproteases comparable to those seen after C10/CCL6 neutralization. These C10/CCL6 and CCR1 manipulations did not alter the production of transgenic IL-13. These studies demonstrate that IL-13 is a potent stimulator of C10/CCL6 and highlight the importance of C10/CCL6 and signaling via CCR1 in the pathogenesis of the IL-13-induced pulmonary phenotype. They also describe a C10/CCL6 target gene cascade in which C10/CCL6 induction is required for optimal IL-13 stimulation of selected chemokines (monocyte chemoattractant protein-1 and MIP-1alpha) and proteases (MMP-2, MMP-9, and cathepsins-K, -L, and -S) and the inhibition of alpha1-antitrypsin.

Anti-respiratory syncytial virus (RSV) neutralizing antibody decreases lung inflammation, airway obstruction, and airway hyperresponsiveness in a murine RSV model

Numerous studies have described a strong association between respiratory syncytial virus (RSV) infection in infancy and the development of recurrent wheezing and airway hyperresponsiveness. We evaluated the effect of an anti-RSV neutralizing monoclonal antibody (palivizumab) on different aspects of RSV disease by using a murine model. BALB/c mice were intranasally inoculated with RSV A2. Palivizumab or an isotype-matched control antibody was administered once at 24 h before inoculation, 1 h after inoculation, or 48 h after inoculation. Regardless of the timing of administration, all mice treated with the neutralizing antibody showed significantly decreased RSV loads in bronchoalveolar lavage (BAL) and lung specimens compared with those of infected controls. Pulmonary histopathologic scores, airway obstruction measured by plethysmography, and airway hyperresponsiveness after methacholine challenge were significantly reduced in mice treated with the anti-RSV antibody 24 h before inoculation compared with those for untreated controls. Concentrations of interferon-gamma, interleukin-10, macrophage inflammatory protein 1alpha, regulated on activation normal T-cell expressed and secreted (RANTES), and eotaxin in BAL fluids were also significantly reduced in mice treated with palivizumab 24 h before inoculation. This study demonstrates that reduced RSV replication was associated with significant modulation of inflammatory and clinical markers of acute disease severity and significant improvement of the long-term pulmonary abnormalities. Studies to determine whether strategies aimed at preventing or reducing RSV replication could decrease the long-term morbidity associated with RSV infection in children should be considered.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases mRNA transcripts in the bronchial secretions of asthmatics

Asthma is a chronic inflammatory disease characterized by profound extracellular matrix changes referred to as bronchial remodelling. In this study, we evaluated matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) mRNA expression in bronchial secretions of asthmatics and correlated MMPs modulations with the lung function as a reflection of the bronchial extracellular matrix remodelling. Quantitative RT-PCR was performed on cell pellets obtained from induced sputum in order to detect the mRNAs for MMP-1, -2, -3, -8, -9, -12, -13 TIMP-1, -2, while semiquantitative RT-PCR was performed to assess the expression of MMP-7, monocyte chemoattractant protein-1 (MCP-1) and transforming growth factor-beta(1) (TGF-beta(1)). The mRNA transcripts for MMP-1, TIMP-1 and monocyte chemoattractant protein-1 (MCP-1) were increased in cell pellets of induced sputum from asthmatics when compared to controls (P<0.05), and the intensity of MMP-1 mRNA expression inversely correlated with the FEV(1) in asthmatics (r=-0.49, P<0.05). The MMP-1 mRNA/TIMP-1 mRNA ratio correlated with the levels of MCP-1 mRNA in asthmatics (r=0.47, P<0.05). There were no differences between the groups with respect to mRNA coding for MMP-2, -3, -7, -8, -9, -12, -13, -14, TIMP-2 and TGF-beta(1). We conclude that cells contained in the bronchial secretions from asthmatics express higher amounts of mRNA for MMP-1 and TIMP-1, perhaps related to an increased expression of MCP-1, which might contribute to the extracellular matrix changes observed during airway remodelling.

Inhibition of stem cell factor reduces pulmonary cytokine levels during allergic airway responses

Stem cell factor (SCF) has a significant role in the inflammation and activation of allergic airway responses. When monoclonal anti-SCF was administered intratracheally during allergen challenge there was a significant alteration of eosinophil accumulation and airway hyperreactivity (AHR). Anti-SCF treatment also attenuated pulmonary cytokine and chemokine levels. In particular, there was an antibody dose-dependent decrease in interleukin (IL)-5 and tumour necrosis factor (TNF)-alpha. There was also a significant reduction of CCL2 and CCL5, which correlated with the reduction in AHR. Mice treated with anti-SCF demonstrated a significant decrease in pulmonary gob-5 gene expression, which has been shown to correlate to goblet cell hyperplasia/metaplasia relating to airway mucus production. Blocking SCF-mediated activation within the airway using a monoclonal antibody indicates that this cytokine may represent a viable target for therapeutic intervention that could affect multiple aspects of allergen-induced immunopathology.

Toll-like receptor 4 contributes to efficient control of infection with the protozoan parasite Leishmania major

The essential role of Toll-like receptors (TLR) in innate immune responses to bacterial pathogens is increasingly recognized, but very little is known about the role of TLRs in host defense against infections with eukaryotic pathogens. For the present study, we investigated whether TLRs contribute to the innate and acquired immune response to infection with the intracellular protozoan parasite Leishmania major. Our results show that TLR4 contributes to the control of parasite growth in both phases of the immune response. We also addressed the mechanism that results in killing or growth of the intracellular parasites. Control of parasite replication correlates with the early induction of inducible nitric oxide synthase in TLR4-competent mice, whereas increased parasite survival in host cells from TLR4-deficient mice correlates with a higher activity of arginase, an enzyme known to promote parasite growth. This is the first study showing that TLR4 contributes to the effective control of Leishmania infection in vivo.

MCP-1 gene regulatory region polymorphism in Chinese children with mild, moderate and near-fatal asthma

BACKGROUND

A polymorphism in the monocyte chemoattractant protein 1 (MCP-1) gene regulatory region has been associated with asthma in Caucasians. This polymorphism is possibly endemic to the Asian region, but its impact on Asian populations is unclear. In addition, the relationship of this marker with life-threatening asthma has not been clarified. The aim of this study was to test the genetic association between the MCP-1 -2518A/G polymorphism and asthma/atopy in a cohort of Chinese children, with particular emphasis on those patients who had experienced life-threatening asthma attacks.

METHODS

Forty-eight children with near-fatal asthma, 134 mild-to-moderate asthmatics, 69 allergic-disorder cases without asthma, and 107 nonasthmatic, nonatopic control children were genotyped by a polymerase chain reaction-based assay.

RESULTS

Comparison of the four groups of children (n = 358) revealed no detectable differences in genotype or allele frequencies of the MCP-1 -2518A/G polymorphism. There was no evidence of association between the polymorphism and any of the outcomes of interest including clinical severity, blood eosinophil count, atopy, total serum IgE levels, and degree of bronchial hyper-responsiveness.

CONCLUSION

These results suggest that the MCP-1 -2518A/G polymorphism is not a risk factor for near-fatal asthma. Furthermore, this polymorphism seems to play no role in the development of asthma or atopy in Chinese subjects, possibly as a result of the genetic heterogeneity between Asian and Caucasian populations with respect to regulation of MCP-1 expression. Our results underscore the necessity of accounting for ethnic background in the investigation of asthma-predisposition genes.

Localization and enhanced mRNA expression of the orphan chemokine receptor L-CCR in the lung in a murine model of ovalbumin-induced airway inflammation

Various CC chemokine receptors are expressed on effector cells in allergic inflammation and their distinct expression pattern may dictate, to a large extent, the migration of inflammatory cells to sites of airway inflammation. The lipopolysaccharide (LPS)-inducible CC chemokine receptor (L-CCR) is an orphan chemokine receptor that has previously been identified in the murine macrophage cell line RAW 264.7 and in murine brain glial cells. In this study we investigated the induction and localization of L-CCR mRNA expression in mouse lung after ovalbumin (OVA)-induced airway inflammation. Both RT-PCR experiments and in situ hybridization (ISH) experiments in whole lung sections revealed a rapid upregulation of L-CCR mRNA expression as early as 1 hr and 3 hr after OVA challenge. Expression was found predominantly in MAC3(+) macrophages and in bronchial epithelium, as shown by ISH and immunohistochemistry (IHC). We demonstrated that L-CCR mRNA expression is strongly upregulated in mouse lung after OVA challenge and is localized in macrophages and bronchial epithelium. Regarding the likely role of L-CCR as a chemokine receptor with the putative ligand monocyte chemotactic protein-1 (MCP-1, CCL2), this receptor may have an important function in the early phase of airway inflammation.

Inhibition of airway inflammation by amino-terminally modified RANTES/CC chemokine ligand 5 analogues is not mediated through CCR3

Chemokines play a key role in the recruitment of activated CD4(+) T cells and eosinophils into the lungs in animal models of airway inflammation. Inhibition of inflammation by N-terminally modified chemokines is well-documented in several models but is often reported with limited dose regimens. We have evaluated the effects of doses ranging from 10 ng to 100 micro g of two CC chemokine receptor antagonists, Met-RANTES/CC chemokine ligand 5 (CCL5) and aminooxypentane-RANTES/CCL5, in preventing inflammation in the OVA-sensitized murine model of human asthma. In the human system, aminooxypentane-RANTES/CCL5 is a full agonist of CCR5, but in the murine system neither variant is able to induce cellular recruitment. Both antagonists showed an inverse bell-shaped inhibition of cellular infiltration into the airways and mucus production in the lungs following allergen provocation. The loss of inhibition at higher doses did not appear to be due to partial agonist activity because neither variant showed activity in recruiting cells into the peritoneal cavity at these doses. Surprisingly, neither was able to bind to the major CCR expressed on eosinophils, CCR3. However, significant inhibition of eosinophil recruitment was observed. Both analogues retained high affinity binding for murine CCR1 and murine CCR5. Their ability to antagonize CCR1 and CCR5 but not CCR3 was confirmed by their ability to prevent RANTES/CCL5 and macrophage inflammatory protein-1beta/CCL4 recruitment in vitro and in vivo, while they had no effect on that induced by eotaxin/CCL11. These results suggest that CCR1 and/or CCR5 may be potential targets for asthma therapy.

Concerted expression of eotaxin-1, eotaxin-2, and eotaxin-3 in human bronchial epithelial cells

Eotaxin-1/CCL11, eotaxin-2/CCL24, and eotaxin-3/CCL26 bind specifically and exclusively to CC chemokine receptor (CCR) 3, which is a potential therapeutic target in treating the peribronchial eosinophilia associated with allergic airway diseases. Bronchial epithelial cells represent an important source of chemokines, and thus we investigated in vitro and in vivo expression of eotaxin-2 and eotaxin-3 in bronchial epithelial cells in comparison with that of eotaxin-1. Immunohistochemistry showed increased expression of both eotaxin-2 and eotaxin-3 in addition to eotaxin-1 in asthmatics. Considerable amounts of eotaxins were secreted by bronchial epithelial lineage. As with eotaxin-1 production, generation of eotaxin-2 and eotaxin-3 by bronchial epithelial cells was up-regulated by IL-4 and IL-13, and attenuated by IFN-gamma and glucocorticoids. In addition to eotaxin-1 expression, but also eotaxin-2 and eotaxin-3 expression in the bronchial epithelium should be taken into consideration when developing the therapeutic strategies to treat eosinophilic airway diseases.

Antagonism of RANTES Receptors Reduces Atherosclerotic Plaque Formation in Mice

Increasing evidence supports the involvement of inflammation in the early phases of atherogenesis. Recruitment of leukocytes within the vascular wall, controlled by chemokines, is an essential process in the development of this common disease. In this study, we report that blocking a chemokine pathway in vivo with the CC chemokine antagonist Met-RANTES reduces the progression of atherosclerosis in a hypercholesterolemic mouse model. The reduction of lesions was correlated with a diminution of expression of several major chemokines and chemokine receptors, a decrease in leukocyte infiltration, and an increase of collagen-rich atheroma, features associated with stable atheroma. Treatment was well tolerated and serum lipid profiles were not affected. Whereas genetically engineered mice with deletion of either a CC chemokine or its receptor have demonstrated resistance to disease, to our knowledge, this is the first demonstration that treatment with a chemokine receptor antagonist limits the progression of atherosclerosis in vivo. Thus, our findings indicate that blockade of chemokine receptor/ligand interactions might become a novel therapeutic strategy to reduce the evolution of this common disease.

Short-term smoke exposure attenuates ovalbumin-induced airway inflammation in allergic mice

Little is known about effects of smoking on airway inflammation in asthma. We tested the hypothesis that smoking enhances established airway inflammation in a mouse model of allergic asthma. C57Bl/6j mice were sensitized to ovalbumin (OVA) and challenged with OVA (OVA-mice) or sham-sensitized to phosphate-buffered saline (PBS) and challenged with PBS aerosols (PBS-mice) for 7 wk. At 4 wk, mice were additionally exposed to air (nonsmoking controls) or mainstream smoke for 3 wk. Using whole body plethysmography, we found OVA-induced bronchoconstriction to be significantly inhibited in smoking OVA-mice as compared with nonsmoking OVA-mice (1 +/- 2% increase versus 22 +/- 6% increase in enhanced pause, respectively). Smoking did not change airway hyperresponsiveness (AHR) to methacholine in PBS-mice, yet significantly attenuated AHR in OVA-mice 24 h after OVA challenge as compared with nonsmoking mice. This was accompanied by reduced eosinophil numbers in lung lavage fluid and tissue of smoking OVA-mice compared with nonsmoking OVA-mice. In contrast to our hypothesis, short-term smoking reduced responsiveness to OVA and methacholine in OVA-mice and decreased airway inflammation when compared with nonsmoking mice. This effect of smoking may be different for long-term smoking, in which remodeling effects of smoking can be expected to interrelate with remodeling changes caused by asthmatic disease.

Regulation of eotaxin gene expression by TNF-alpha and IL-4 through mRNA stabilization: involvement of the RNA-binding protein HuR

During inflammatory responses, a major posttranscriptional regulation of early response and inflammatory gene expression occurs through modulation of mRNA turnover. We report that two potent inducers of the CC chemokine eotaxin, TNF-alpha and IL-4, regulate its production in airway epithelial cells by increasing eotaxin mRNA stability. In experiments using the transcriptional inhibitor actinomycin D, eotaxin mRNA half-life was significantly prolonged by cell stimulation with TNF-alpha or IL-4, with the combination of the two cytokines being the most effective in extending the mRNA half-life. Involvement of the eotaxin 3' untranslated region in the mRNA-stabilizing effect was tested by transient transfection of a construct expressing a chimeric transcript carrying a serum-inducible beta-globin reporter linked to the eotaxin 3' untranslated region. The half-life of the chimeric mRNA was markedly increased in cells stimulated with TNF-alpha and IL-4. Evidence that the mRNA-stabilizing protein HuR participated in the cytokine effect was obtained: first, HuR presence in the cytoplasm, believed to be required for HuR-mediated mRNA stabilization, increased in both transformed (BEAS-2B cell line) and primary bronchial epithelial cells following treatment with TNF-alpha and IL-4. Second, endogenous eotaxin mRNA was found to bind to HuR in vivo, as detected by immunoprecipitation of HuR-containing messenger ribonucleoprotein complexes followed by real-time RT-PCR analysis; such association increased after cell treatment with TNF-alpha and IL-4. Third, overexpression of HuR in BEAS-2B cells significantly increased the expression of eotaxin mRNA and protein. Our findings implicate mRNA stabilization in the cytokine-mediated increase in eotaxin expression and strongly suggest a role for HuR in this effect.

Eotaxin-2 and IL-5 cooperate in the lung to regulate IL-13 production and airway eosinophilia and hyperreactivity

BACKGROUND

Eotaxin-2 is a member of the eotaxin subfamily of CC chemokines that display eosinophil-specific, chemotactic properties and has been associated with allergic disorders. However, the contribution of eotaxin-2 to the development of defined pathogenic features of allergic disease remains to be defined.

OBJECTIVE

We sought to determine whether eotaxin-2 was a cofactor with IL-5 for the regulation of pulmonary eosinophilia and to identify the combined role of these molecules in the induction of phenotypic characteristics of allergic lung disease.

METHODS

We instilled recombinant eotaxin-2 into the airways of wild-type mice that had been treated systemically with IL-5 or into IL-5-transgenic mice and characterized pulmonary eosinophil numbers, IL-13 production, and airway hyperreactivity (AHR) to methacholine. Mice deficient in the IL-4 receptor alpha-chain, IL-13, and signal transducers and activators of transcription 6 or mice treated with anti-CCR3 monoclonal antibody were also used.

RESULTS

Eotaxin-2 and IL-5 cooperatively promoted eosinophil accumulation, IL-13 production, and AHR to methacholine. Neither eotaxin-2 nor IL-5 alone induced these features of allergic disease. IL-13 production was critically dependent on eotaxin-2- and IL-5-regulated eosinophilia, which predisposed to the development of AHR. AHR was dependent on IL-13 and signaling through the IL-4R alpha-chain and signal transducers and activators of transcription 6 pathways and the presence of eosinophils in the lung.

CONCLUSION

These investigations demonstrate important cooperativity between eotaxin-2, IL-5, and IL-13 signaling systems and eosinophils for the development of hallmark features of allergic disease of the lung.

Role of Monocyte Chemotactic Protein-1/CC Chemokine Ligand 2 on γδ T Lymphocyte Trafficking during Inflammation Induced by Lipopolysaccharide orMycobacterium bovisBacille Calmette-Guérin

Gammadelta T lymphocytes are involved in a great variety of inflammatory and infectious responses. However, the mechanisms by which gammadelta T lymphocytes migrate to inflamed sites are poorly understood. In this study we investigate the role of monocyte chemotactic protein (MCP)-1 in regulating gammadelta T cell migration after LPS or Mycobacterium bovis bacille Calmette-Guérin (BCG) challenge. LPS-induced gammadelta T cell influx was significantly inhibited by either pretreatment with dexamethasone or vaccinia virus Lister 35-kDa chemokine binding protein, vCKBP, a CC chemokine neutralizing protein, suggesting a role for CC chemokines in this phenomenon. LPS stimulation increased the expression of MCP-1 mRNA and protein at the inflammation site within 6 h. It is noteworthy that LPS was unable to increase MCP-1 production or gammadelta T cell recruitment in C3H/HeJ, indicative of the involvement of Toll-like receptor 4. Gammadelta T cells express MCP-1 receptor CCR2. Pretreatment with anti-MCP-1 mAb drastically inhibited LPS-induced in vivo gammadelta T cell mobilization. Indeed, MCP-1 knockout mice were unable to recruit gammadelta T cells to the pleural cavity after LPS stimulation, effect that could be restored by coadministration of MCP-1. In addition, BCG-induced gammadelta lymphocyte accumulation was significantly reduced in MCP-1 knockout mice when compared with wild-type mice. In conclusion, our results indicate that LPS-induced gammadelta T lymphocyte migration is dependent on Toll-like receptor 4 and sensitive to both dexamethasone and CC chemokine-binding protein inhibition. Moreover, by using MCP-1 neutralizing Abs and genetically deficient mice we show that LPS- and BCG-induced gammadelta T lymphocyte influx to the pleural cavity of mice is mainly orchestrated by the CC chemokine MCP-1.

The role of chemokines and chemokine receptors in eosinophil activation during inflammatory allergic reactions

Chemokines are important chemotactic cytokines that play a fundamental role in the trafficking of leukocytes to sites of inflammation. They are also potent cell-activating factors, inducing cytokine and histamine release and free radical production, a fact that makes them particularly important in the pathogenesis of allergic inflammation. The action of chemokines is regulated at the level of agonist production and processing as well as at the level of receptor expression and coupling. Therefore, an analysis of the ligands must necessarily consider receptors. Eosinophils are target cells involved in the allergic inflammatory response since they are able to release a wide variety of mediators including CC and CXC chemokines and express their receptors. These mediators could damage the airway epithelial cells and might be important to stimulate other cells inducing an amplification of the allergic response. This review focuses on recently emerging data pertaining to the importance of chemokines and chemokine receptors in promoting eosinophil activation and migration during the allergic inflammatory process. The analysis of the function of eosinophils and their chemokine receptors during allergic inflammation might be a good approach to understanding the determinants of asthma severity and to developing novel therapies.

Chemokines in allergic airway disease

Expression of chemokine receptors on T helper 2 cells and eosinophils has been postulated to be the mechanism by which these cells are selectively recruited to the lung during allergic inflammatory reactions. Mouse models have provided evidence to show that blocking the ligands for these receptors is successful in abrogating the pathophysiological effects of allergen challenge. However, recent studies describing the effect of genetic deletions of these chemokine receptors have not confirmed the results obtained with ligand knockouts or neutralising antibodies. Coupled with the realisation that, because of a lack of species cross-reactivity, it is not possible to test small molecule antagonists against human receptors in the original in vivo animal models, the future of chemokine receptor therapeutics is in question. However, recent advances have been made regarding the therapeutic potential of blocking the chemokine receptors CCR3, CCR4 and CCR8 in allergic airway disease.

Role of regulator of G protein signaling 16 in inflammation-induced T lymphocyte migration and activation

Chemokine-induced T lymphocyte recruitment to the lung is critical for allergic inflammation, but chemokine signaling pathways are incompletely understood. Regulator of G protein signaling (RGS)16, a GTPase accelerator (GTPase-activating protein) for Galpha subunits, attenuates signaling by chemokine receptors in T lymphocytes, suggesting a role in the regulation of lymphocyte trafficking. To explore the role of RGS16 in T lymphocyte-dependent immune responses in a whole-organism model, we generated transgenic (Tg) mice expressing RGS16 in CD4(+) and CD8(+) cells. rgs16 Tg T lymphocytes migrated to CC chemokine ligand 21 or CC chemokine ligand 12 injection sites in the peritoneum, but not to CXC chemokine ligand 12. In a Th2-dependent model of allergic pulmonary inflammation, CD4(+) lymphocytes bearing CCR3, CCR5, and CXCR4 trafficked in reduced numbers to the lung after acute inhalation challenge with allergen (OVA). In contrast, spleens of sensitized and challenged Tg mice contained increased numbers of CD4(+)CCR3(+) cells producing more Th2-type cytokines (IL-4, IL-5, and IL-13), which were associated with increased airway hyperreactivity. Migration of Tg lymphocytes to the lung parenchyma after adoptive transfer was significantly reduced compared with wild-type lymphocytes. Naive lymphocytes displayed normal CCR3 and CXCR4 expression and cytokine responses, and compartmentation in secondary lymphoid organs was normal without allergen challenge. These results suggest that RGS16 may regulate T lymphocyte activation in response to inflammatory stimuli and migration induced by CXCR4, CCR3, and CCR5, but not CCR2 or CCR7.

Matrix metalloproteinase-9-mediated dendritic cell recruitment into the airways is a critical step in a mouse model of asthma

Dendritic cells (DCs) appear to be strategically implicated in allergic diseases, including asthma. Matrix metalloproteinase (MMP)-9 mediates transmigration of inflammatory leukocytes across basement membranes. This study investigated the role of MMP-9 in airway DC trafficking during allergen-induced airway inflammation. MMP-9 gene deletion affected the trafficking of pulmonary DCs in a specific way: only the inflammatory transmigration of DCs into the airway lumen was impaired, whereas DC-mediated transport of airway Ag to the thoracic lymph nodes remained unaffected. In parallel, the local production of the Th2-attracting chemokine CC chemokine ligand 17/thymus and activation-regulated chemokine, which was highly concentrated in purified lung DCs, fell short in the airways of allergen-exposed MMP-9(-/-) mice. This was accompanied by markedly reduced peribronchial eosinophilic infiltrates and impaired allergen-specific IgE production. We conclude that the specific absence of MMP-9 activity inhibits the development of allergic airway inflammation by impairing the recruitment of DCs into the airways and the local production of DC-derived proallergic chemokines.

Therapeutic efficacy of adoptive immunotherapy is predicated on in vivo antigen-specific proliferation of donor T cells

Activated T cells with down-regulated L-selectin expression (L-sel(-)) from tumor-draining lymph nodes represent a potent source of specific immune effectors in adoptive immunotherapy. Using congenic pairs of mice and carboxyfluorescein diacetate succinimidyl ester-labeled L-sel(-) T cells, the current study analyzed in vivo proliferation of transferred cells. In the lung of MCA205 tumor-bearing mice, 6% or 0.3 x 10(6) of the 5 x 10(6) donor cells were identified 24 h after transfer. Vigorous proliferation of donor cells was evident on day 2, reaching a maximum on day 6. The proliferation was tumor-specific and CD4 T cells divided with greater magnitude than CD8 cells. Successful adoptive immunotherapy also required sublethal whole-body irradiation (WBI) of the recipient. WBI exerted its effects on facilitating specific T cell proliferation at the tumor site. Taken together, our results demonstrate that adoptively transferred T cells undergo extensive proliferation in response to the tumor and this response is associated with therapeutic efficacy.

Preferential signaling and induction of allergy-promoting lymphokines upon weak stimulation of the high affinity IgE receptor on mast cells

Mast cell degranulation and de novo cytokine production is a consequence of antigen-aggregation of the immunoglobulin E (IgE)-occupied high affinity receptor for IgE (Fc epsilon RI). Herein, we report that lymphokines that promote allergic inflammation, like MCP-1, were potently induced at low antigen (Ag) concentrations or at low receptor occupancy with IgE whereas some that down-regulate this response, like interleukin (IL)-10, required high receptor occupancy. Weak stimulation of mast cells caused minimal degranulation whereas a half-maximal secretory response was observed for chemokines and, with the exception of TNF-alpha, a weaker cytokine secretory response was observed. The medium from weakly stimulated mast cells elicited a monocyte/macrophage chemotactic response similar to that observed at high receptor occupancy. Weak stimulation also favored the phosphorylation of Gab2 and p38MAPK, while LAT and ERK2 phosphorylation was induced by a stronger stimulus. Gab2-deficient mast cells were severely impaired in chemokine mRNA induction whereas LAT-deficient mast cells showed a more pronounced defect in cytokines. These findings demonstrate that perturbation of small numbers of IgE receptors on mast cells favors certain signals that contribute to a lymphokine response that can mediate allergic inflammation.

Lung CD25 CD4 regulatory T cells suppress type 2 immune responses but not bronchial hyperreactivity

To study the effects of chronic Ag deposition in the airway mucosa on CD4(+) T cell priming and subsequent airway disease, transgenic mice were generated that expressed OVA under the control of the surfactant protein C promoter. CD4 T cells from these mice were tolerant to OVA but this was overcome among spleen CD4 T cells by crossing to OVA-specific DO11.10 TCR-transgenic mice. Lungs from the double-transgenic mice developed lymphocytic infiltrates and modest mucus cell hyperplasia. Infiltrating cells were unaffected by the absence of either Rag-1 or Stat6, although the latter deficiency led to the disappearance of mucus. In the lung of double-transgenic mice, a large number of Ag-specific CD4 T cells expressed CD25 and functioned as regulatory T cells. The CD25(+) CD4 T cells suppressed proliferation of CD25(-) CD4 T cells in vitro and inhibited type 2 immune responses induced by aerosolized Ags in vivo. Despite their ability to suppress allergic type 2 immunity in the airways, however, CD25(+) CD4 regulatory T cells had no effect on the development of bronchial hyperreactivity.

Significant involvement of CCL2 (MCP-1) in inflammatory disorders of the lung

Mounting evidence suggests that CCL2 (MCP-1) and its hematopoietic cell receptor CC chemokine receptor 2 (CCR2) are involved in inflammatory disorders of the lung. In animal models of allergic asthma, idiopathic pulmonary fibrosis (IPF), and bronchiolitis obliterans syndrome (BOS), CCL2 expression and protein production are increased and the disease process is attenuated by CCL2 immunoneutralization. Mechanisms by which CCL2 may be acting include recruitment of regulatory and effector leukocytes; stimulation of histamine or leukotriene release from mast cells or basophils; induction of fibroblast production of transforming growth factor-beta (TGF-beta) and procollagen; and enhancement of Th2 polarization. Recently, polymorphism for CCL2 has been described with increased cytokine-induced release of CCL2 by monocytes and increased risk of allergic asthma. These studies identify potentially important roles for CCL2 in these lung inflammatory disorders. While CCL2 inhibition in patients with acute respiratory distress syndrome (ARDS) may be hazardous by interfering with defense against bacteremia, future studies are needed to determine if CCL2/CCR2 antagonism will offer breakthrough therapy for patients with allergic asthma, IPF, or BOS, and to confirm the hypothesis that CCL2 polymorphism places patients at greater risk for these disorders.

Monocyte chemoattractant protein-1 (CCL2) in inflammatory disease and adaptive immunity: therapeutic opportunities and controversies

Monocyte chemoattractant protein (MCP)-1 (CCL2) specifically attracts monocytes and memory T cells. Its expression occurs in a variety of diseases characterized by mononuclear cell infiltration, and there is substantial biological and genetic evidence for its essential role in atherosclerosis and multiple sclerosis. Despite intensive screening, there are as yet no small-molecule antagonists of the receptor of MCP-1/CCL2, CCR2. However, biological agents, including antibodies and inhibitory peptides, have been developed and may be useful for these indications. Recent evidence from genetically modified mice indicates that MCP-1 and CCR2 have unanticipated effects on T helper (Th) cell development. However, unlike the identical phenotypes of MCP-1/CCL2(-/-) and CCR2(-/-) mice in inflammatory diseases, the phenotypes of these mice are disparate in adaptive immunity: MCP-1 stimulates Th2 polarization, whereas CCR2 activation stimulates Th1 polarization. This presents both a challenge and an opportunity for targeting the MCP-1/CCL2/CCR2 axis in disease.

Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: role of eosinophils, IL-5, eotaxin, and IL-13

BACKGROUND

Glucocorticoids inhibit allergen-induced airway eosinophilia and airway hyperresponsiveness (AHR). Whether glucocorticoids mediate their effects on AHR by inhibiting eotaxin and IL-5, 2 of the principal mediators of eosinophilia, or through IL-13, an important mediator of AHR, has not been established.

OBJECTIVE

We sought to investigate the effects of glucocorticoids on airway eosinophilia and the expression of IL-5, eotaxin, and IL-13 in relation to the induction of AHR in a murine model of allergic asthma.

METHODS

Dexamethasone (4 mg/kg) and mAbs against eotaxin (80 micro g/kg) and IL-5 (100 micro g/kg) singly and in combination were administered to immunized mice before antigen challenge. Airway responsiveness to methacholine was measured in anesthetized and mechanically ventilated animals. Eotaxin, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), lung homogenates, or both were measured by means of ELISA.

RESULTS

A single antigen challenge induced AHR that lasted at least 10 days. Eotaxin protein and mRNA levels increased in lung tissue but not in BALF after challenge. IL-5 protein and mRNA levels increased both in BALF and in lung tissue. Dexamethasone reduced airway eosinophilia, AHR, and protein and mRNA for eotaxin and IL-5. Anti-murine eotaxin and anti-IL-5 antibodies alone and in combination reduced the ovalbumin-induced airway eosinophilia significantly but failed to inhibit AHR. Both dexa-methasone and anti-IL-5/anti-eotaxin inhibited the increases in lung IL-13 levels after ovalbumin challenge to a similar extent.

CONCLUSION

These findings suggest that the inhibition of AHR by the glucocorticoid dexamethasone does not appear to be explained by effects on eosinophilia, eotaxin, IL-5, or IL-13.

Antimicrobial and immunologic activities of clarithromycin in a murine model of Mycoplasma pneumoniae-induced pneumonia

Because macrolide antibiotics are hypothesized to possess immunomodulatory activity independent of their antimicrobial activity, we evaluated the immunomodulatory effect of clarithromycin in a murine model of lung inflammation induced by either live or UV-killed Mycoplasma pneumoniae. BALB/c mice were intranasally inoculated once with live or UV-killed M. pneumoniae. Clarithromycin (25 mg/kg of body weight) or placebo was subcutaneously administered once daily in both groups of mice. In mice infected with live M. pneumoniae, clarithromycin treatment significantly reduced quantitative M. pneumoniae bronchoalveolar lavage (BAL) culture, pulmonary histopathologic scores (HPS), and airway resistance-obstruction (as measured by plethysmography) compared with placebo. Concentrations of tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), mouse KC (functional IL-8), JE/MCP-1, and MIP-1alpha in BAL fluid were also significantly decreased in mice infected with live M. pneumoniae given clarithromycin. In contrast, mice inoculated with UV-killed M. pneumoniae had no significant reduction in HPS, airway resistance-obstruction, or BAL cytokine or chemokine concentrations in response to clarithromycin administration. Clarithromycin therapy demonstrated beneficial effects (microbiologic, histologic, respiratory, and immunologic) on pneumonia in the mice infected with live M. pneumoniae; this was not observed in the mice inoculated with UV-killed M. pneumoniae.

A new murine model of islet xenograft rejection: graft destruction is dependent on a major histocompatibility-specific interaction between T-cells and macrophages

A new murine model of porcine islet-like cell cluster (ICC) xenograft rejection, avoiding interference of unspecific inflammation, was introduced and used to investigate rejection mechanisms. Athymic (nu/nu) mice were transplanted with syngeneic, allogeneic, or xenogeneic islets under the kidney capsule. After the original transplantation, immune cells in porcine ICC xenografts undergoing rejection in native immunocompetent mice were transferred to the peritoneal cavity of the athymic mice. At defined time points after transfer, the primary grafts were evaluated by immunohistochemistry and real-time quantitative RT-PCR to estimate cytokine and chemokine mRNA expression. Transfer of immunocompetent cells enabled athymic (nu/nu) mice to reject a previously tolerated ICC xenograft only when donor and recipient were matched for major histocompatibility complex (MHC). In contrast, allogeneic and syngeneic islets were not rejected. The ICC xenograft rejection was mediated by transferred T-cells. The main effector cells, macrophages, were shown to be part of a specific immune response. By day 4 after transplantation, there was an upreglation of both Th1- and Th2-associated cytokine transcripts. The transferred T-cells were xenospecific and required MHC compatibility to induce rejection. Interaction between the TCR of transferred T-cells and MHC on host endothelial cells and/or macrophages seems necessary for inducing ICC xenograft rejection.

CC chemokine ligand 1 promotes recruitment of eosinophils but not Th2 cells during the development of allergic airways disease

One of the characteristic features of allergic asthma is recruitment of large numbers of inflammatory cells including eosinophils and Th2 lymphocytes to the lung. This influx of inflammatory cells is thought to be a controlled and coordinated process mediated by chemokines and their receptors. It is thought that distinct, differential expression of chemokine receptors allows selective migration of T cell subtypes in response to the chemokines that bind these receptors. Th2 cells preferentially express CCR8 and migrate selectively to its ligand, CC chemokine ligand (CCL)1. We studied the role of the CCR8 ligand, CCL1, in the specific recruitment of Th2 cells and eosinophils to the lung in a murine model of allergic airway disease. We have demonstrated for the first time that CCL1 is up-regulated in the lung following allergen challenge. Moreover, a neutralizing Ab to CCL1 reduced eosinophil migration to the lung, but had no effect on recruitment of Th2 cells following allergen challenge. In addition, there was no change in airway hyperresponsiveness or levels of Th2 cytokines. In a Th2 cell transfer system of pulmonary inflammation, anti-CCL1 also failed to affect recruitment of Th2 cells to the lung following allergen challenge. Significantly, intratracheal instillation of rCCL1 increased recruitment of eosinophils but not Th2 cells to the lung in allergen-sensitized and -challenged mice. In summary, our results indicate that CCL1 is important for the pulmonary recruitment of eosinophils, rather than allergen-specific Th2 cells, following allergen challenge.

IL-5 and eotaxin levels in middle ear effusion and blood from asthmatics with otitis media with effusion

OBJECTIVE

The purpose of this study was to evaluate eosinophil infiltration as well as IL-5 and eotaxin levels in middle ear effusion (MEE) and blood from otitis media with effusion (OME) patients with asthma and to compare the findings with those from OME patients without asthma (control group).

MATERIAL AND METHODS

Levels of IL-5 and eotaxin in MEE and blood were measured by means of enzyme-linked immunosorbent assay.

RESULTS

5 levels in MEE were significantly higher than those in blood in both groups of patients and in OME patients with asthma than in the control group. In addition, in OME patients with asthma, there was a significant correlation between the percentage of eosinophils and IL-5 levels in MEE. Eotaxin levels in blood were significantly higher than those in MEE in both groups of patients and in OME patients with asthma than in the control group. In addition, in OME patients with asthma, the percentage of eosinophils and eotaxin levels in blood tended to correlate, but did not reach statistical significance.

CONCLUSION

These data suggest that, in OME patients with asthma, eosinophilia in MEE depends more on IL-5 than on eotaxin, and that eotaxin may play an important role in the mobilization of eosinophils from the bone marrow into the blood.

Chemokines and their receptors in asthma and chronic obstructive pulmonary disease

Recruitment of inflammatory cells into the airways is a critical event that triggers and sustains the clinical manifestations of asthma and chronic obstructive pulmonary disease. Since the identification of the family of chemotactic cytokines, known as chemokines, as critical regulators of cell trafficking in the immune system, these molecules have come to the center stage in the field of inflammation and immunity. The goal of this article will be to summarize the recent developments in our understanding of the complex role that chemokines play in the pathogenesis of asthma and COPD.

The role of chemokines and their receptors in the rejection of pig islet tissue xenografts

The mechanism by which inflammatory cells are recruited to pig islet tissue (proislet) xenografts was investigated by examining the intragraft mRNA expression of murine alpha- and beta-chemokines in CBA/H mice from days 3 to 10 post-transplant. Xenograft rejection was associated with early intragraft transcript expression for monocyte chemotactic protein-1 (MCP-1) (3 to 5 days), IP-10 (3 to 4 days) and macrophage inflammatory protein-1alpha (MIP-1alpha) (3 to 5 days) and subsequent expression of eotaxin (days 4 to 10), MIP-1beta (days 4 and 5) and regulated on activation, normal T cell expressed and secreted (RANTES) (days 4 to 6) mRNA. This pattern was consistent with the early recruitment of macrophages (MCP-1, MIP-1alpha), the influx of CD4 T cells (MCP-1, MIP-1alpha, MIP-1beta, IP-10 and RANTES) and the characteristic infiltrate of eosinophils (eotaxin and RANTES) associated with islet xenograft rejection. Inhibition of beta-chemokine signaling in CCR2-/- mice (which lack the major co-receptor for MCP-1) resulted in retarded macrophage and CD4 T cell recruitment, enhanced eosinophil influx and a minor delay in rejection, compared with wildtype mice; there was little effect on leukocyte infiltration in xenografts harvested from CCR5-/- mice (lacking the co-receptor for MIP-1alpha, MIP-1beta and RANTES). The impeded migration of leukocytes into xenografts in CCR2-/- hosts was associated with delayed intragraft expression of MCP-1 and RANTES mRNA; absence of MCP-1/CCR2-mediated signaling led to enhanced intragraft expression of MCP-1, MIP-1alpha and MIP-1beta mRNA. These findings suggest that MCP-1 plays an important role in regulating macrophage and CD4 T cell infiltration to xenograft sites via the CCR2 signaling pathway. Additional treatment of xenografted CCR2-/- transplant recipients with anti-interleukin-(IL)-4 and anti-IL-5 mAbs further delayed xenograft rejection demonstrating the potential for combined antirejection strategies in facilitating pig islet xenotransplantation.

Absence of CCR8 does not impair the response to ovalbumin-induced allergic airway disease

Interaction of chemokines with their specific receptors results in tight control of leukocyte migration and positioning. CCR8 is a chemokine receptor expressed mainly in CD4(+) single-positive thymocytes and Th2 cells. We generated CCR8-deficient mice (CCR8(-/-)) to study the in vivo role of this receptor, and describe in this study the CCR8(-/-) mouse response in OVA-induced allergic airway disease using several models, including an adoptive transfer model and receptor-blocking experiments. All CCR8(-/-) mice developed a pathological response similar to that of wild-type animals with respect to bronchoalveolar lavage cell composition, peripheral blood and bone marrow eosinophilia, lung infiltrates, and Th2 cytokine levels in lung and serum. The results contrast with a recent report using one of the OVA-induced asthma models studied here. Similar immune responses were also observed in CCR8(-/-) and wild-type animals in a different model of ragweed allergen-induced peritoneal eosinophilic inflammation, with an equivalent number of eosinophils and analogous increased levels of Th2 cytokines in peritoneum and peripheral blood. Our results show that allergic diseases course without critical CCR8 participation, and suggest that further work is needed to unravel the in vivo role of CCR8 in Th2-mediated pathologies.

Involvement of CCR3-reactive chemokines in eosinophil survival

BACKGROUND

Although eosinophils undergo apoptosis and are thus eliminated from sites of inflammation, they survive longer if survival factors, such as IL-3, IL-5 and GM-CSF, are present. However, it is often observed that some eosinophils survive even when incubated without any survival factors (spontaneous survival). The aim of the present study was to investigate what kind of factor(s) is associated with this spontaneous survival of eosinophils.

METHODS

Eosinophils were purified from bronchoalveolar lavage of antigen-exposed Balb/c mice and stained with propidium iodide to detect apoptotic ones.

RESULTS

We found that the spontaneous survival of eosinophils was reduced by treatment of the cells with anti-CC chemokine receptor-3 (CCR3) antibody (Ab). Moreover, eotaxin-1, eotaxin-2, and eotaxin-3 all prolonged the survival of eosinophils in a dose-dependent fashion. The survival-prolonging effect of eotaxin-1 was enhanced in the presence of eotaxin-3, indicating that these chemokines might work synergistically.

CONCLUSION

We speculate that eosinophils survive longer under the influence of CCR3-reactive chemokines, which aid the infiltration of these cells into the tissue and that eosinophils may survive even longer if they encounter survival factors at local inflammatory sites.

Leukotrienes, IL-13, and chemokines cooperate to induce BHR and mucus in allergic mouse lungs

In mice, intratracheal challenges with antigen (ovalbumin) or recombinant murine interleukin-13 (IL-13) induce lung inflammation, bronchial hyperreactivity (BHR), and mucus accumulation as independent events (Singer M, Lefort J, and Vargaftig BB. Am J Respir Cell Mol Biol 26: 74-84, 2002), largely mediated by leukotrienes (LT). We previously showed that LTC(4) was released 15 min after ovalbumin, and we show that it induces the expression of monocyte chemoattractant proteins 1 and 5 and KC in the lungs, as well as IL-13 mRNA. Instilled intratracheally, these chemokines induced BHR and mucus accumulation, which were inhibited by the 5-lipoxygenase inhibitor zileuton and by the cysteinyl-LT receptor antagonist MK-571, suggesting mediation by cysteinyl-LT. Because these chemokines also induced release of LT into the bronchoalveolar lavage fluid and IL-13 into the lungs, we hypothesize that LT- and chemokine-based loops for positive-feedback regulations cooperate to maintain and amplify BHR and lung mucus accumulation after allergic challenge and in situations where IL-13, LT, or chemokines are generated.

Chemokines in asthma: cooperative interaction between chemokines and IL-13

The asthmatic response is characterized by elevated production of IgE, cytokines, chemokines, mucus hypersecretion, air-way obstruction, eosinophilia, and enhanced airway hyperreactivity to spasmogens. Clinical and experimental investigations have demonstrated a strong correlation between the presence of CD4+ TH2 cells, eosinophils, and disease severity, suggesting an integral role for these cells in the pathophysiology of asthma. TH2 cells are thought to induce asthma through the secretion of an array of cytokines (IL-4, -5, -9 -1),-13, -25) that activate inflammatory and residential effector pathways both directly and indirectly. In particular, IL-4 and IL-13 are produced at elevated levels in the asthmatic lung and are thought to be central regulators of many of the hallmark features of the disease. The potency of IL-13 in promoting airway hyperreactivity and mucus hypersecretion and the ability of IL-13 blockade to abrogate several critical aspects of experimental asthma have led to the view that this is a critical cytokine in disease pathogenesis. Extensive studies have also demonstrated a central role for chemokines in orchestrating multiple aspects of the asthmatic response. Chemokines are potent leukocyte chemoattractants, cellular activating factors, and histamine-releasing factors, which makes them particularly important in the pathogenesis of allergic inflammation. In particular, the eotaxin subfamily of chemokines and their receptor CC chemokine receptor 3 have emerged as central regulators of the asthmatic response. Recent studies have provided an integrated mechanism by which to explain the coordinate interaction between IL-13 and chemokines in the pathogenesis of asthma. In this regard, chemokines and IL-13 are attractive new therapeutic targets for the treatment of allergic disease. This article focuses on recently emerging data pertaining to the importance of chemokines, especially eotaxins, in promoting IL-13-associated allergic lung responses, as well as the potential for pharmacologically targeting these pathways.

Chemokine receptors in inflammation: an overview

Chemokine receptors play a key role in directing the migration of inflammatory cells into various injured or infected organs. However, migration of inflammatory cells into tissues can in itself be a cause and amplifier of tissue damage and disease, particularly in chronic autoimmune or allergic disorders. On this basis, much effort is currently devoted at the identification of molecular signals regulating the recruitment of inflammatory cells into tissues and at developing novel strategies to inhibit discrete pathways in this process. Great progress has recently been made in identification of a number of chemokine receptors involved in the process of leukocyte migration. The challenge is now to elucidate the specific contribution and involvement of the different receptors in distinct inflammatory processes and diseases and to prove that interference with any of these pathways may lead to development of novel therapeutics.