CCR9 Is a Key Regulator of Early Phases of Allergic Airway Inflammation.

Airway inflammation is the most common hallmark of allergic asthma. Chemokine receptors involved in leukocyte recruitment are closely related to the pathology in asthma. CCR9 has been described as a homeostatic and inflammatory chemokine receptor, but its role and that of its ligand CCL25 during lung inflammation remain unknown. To investigate the role of CCR9 as a modulator of airway inflammation, we established an OVA-induced allergic inflammation model in CCR9-deficient mice. Here, we report the expression of CCR9 and CCL25 as early as 6 hours post-OVA challenge in eosinophils and T-lymphocytes. Moreover, in challenged CCR9-deficient mice, cell recruitment was impaired at peribronchial and perivenular levels. OVA-administration in CCR9-deficient mice leads to a less inflammatory cell recruitment, which modifies the expression of IL-10, CCL11, and CCL25 at 24 hours after OVA challenge. In contrast, the secretion of IL-4 and IL-5 was not affected in CCR9-deficient mice compared to WT mice. These results demonstrate for the first time that CCR9 and CCL25 expressions are induced in the early stages of airway inflammation and they have an important role modulating eosinophils and lymphocytes recruitment at the first stages of inflammatory process, suggesting that they might be a potential target to regulate inflammation in asthma.

Neonatal respiratory syncytial virus infection has an effect on lung inflammation and the CD4(+) CD25(+) T cell subpopulation during ovalbumin sensitization in adult mice.

In BALB/c adult mice, respiratory syncytial virus (RSV) infection enhances the degree of lung inflammation before and/or after ovalbumin (OVA) respiratory sensitization. However, it is unclear whether RSV infection in newborn mice has an effect on the immune response to OVA respiratory sensitization in adult mice. The aim of this study was to determine if RSV neonatal infection alters T CD4(+) population and lung inflammation during OVA respiratory sensitization in adult mice. BALB/c mice were infected with RSV on the fourth day of life and challenged by OVA 4 weeks later. We found that in adult mice, RSV neonatal infection prior to OVA sensitization reduces the CD4(+) CD25(+) and CD4(+) CD25(+) forkhead protein 3 (FoxP3)(+) cell populations in the lungs and bronchoalveolar lavage. Furthermore, it also attenuates the inflammatory infiltrate and cytokine/chemokine expression levels in the mouse airways. In conclusion, the magnitude of the immune response to a non-viral respiratory perturbation in adult mice is not enhanced by a neonatal RSV infection.

A CCL chemokine-derived peptide (CDIP-2) exerts anti-inflammatory activity via CCR1, CCR2 and CCR3 chemokine receptors: Implications as a potential therapeutic treatment of asthma.

Allergic asthma is a chronic inflammatory disease characterized by the accumulation of eosinophils, Th2 cells and mononuclear cells in the airways, leading to changes in lung architecture and subsequently reduced respiratory function. We have previously demonstrated that CDIP-2, a chemokine derived peptide, reduced in vitro chemotaxis and decreased cellular infiltration in a murine model of allergic airway inflammation. However, the mechanisms involved in this process have not been identified yet. Now, we found that CDIP-2 reduces chemokine-mediated functions via interactions with CCR1, CCR2 and CCR3. Moreover, using bone marrow-derived eosinophils, we demonstrated that CDIP-2 modifies the calcium fluxes induced by CCL11 and down-modulated CCR3 expression. Finally, CDIP-2 treatment in a murine model of OVA-induced allergic airway inflammation reduced leukocyte recruitment and decreases production of cytokines. These data suggest that chemokine-derived peptides represent new therapeutic tools to generate more effective antiinflammatory drugs.

The multiple faces of CCL13 in immunity and inflammation.

CCL13/MCP-4, is a CC family chemokine that is chemoattractant for eosinophils, basophils, monocytes, macrophages, immature dendritic cells, and T cells, and its capable of inducing crucial immuno-modulatory responses through its effects on epithelial, muscular and endothelial cells. Similar to other CC chemokines, CCL13 binds to several chemokine receptors (CCR1, CCR2 and CCR3), allowing it to elicit different effects on its target cells. A number of studies have shown that CCL13 is involved in many chronic inflammatory diseases, in which it functions as a pivotal molecule involved in the selective recruitment of cell lineages to the inflamed tissues and their subsequent activation. Based on these studies, we suggest that blocking the actions of CCL13 can serve as a novel strategy for the generation of agents with anti-inflammatory activity. The main goal of this review is to present the current information about CCL13, its gene and protein structure and the roles of this chemokine during innate/adaptive immune responses in inflammatory diseases.

CCR9+ T cells contribute to the resolution of the inflammatory response in a mouse model of intestinal amoebiasis.

Analysis of the mechanisms underlying the inflammatory response in amoebiasis is important to understand the immunopathology of the disease. Mucosal associated effector and regulatory T cells may play a role in regulating the inflammatory immune response associated to Entamoeba histolytica infection in the colon. A subpopulation of regulatory T cells has recently been identified and is characterized by the expression of the chemokine receptor CCR9. In this report, we used CCR9 deficient (CCR9(-/-)) mice to investigate the role of the CCR9(+) T cells in a murine model of E. histolytica intestinal infection. Intracecal infection of CCR9(+/+), CCR9(+/-) and CCR9(-/-) mice with E. histolytica trophozoites, revealed striking differences in the development and nature of the intestinal inflammatory response observed between these strains. While CCR9(+/+) and CCR9(+/-) mice were resistant to the infection and resolved the pathogen-induced inflammatory response, CCR9(-/-) mice developed a chronic inflammatory response, which was associated with over-expression of the cytokines IFN-γ, TNF-α, IL-4, IL-6 and IL-17, while IL-10 was not present. In addition, increased levels of CCL11, CCL20 and CCL28 chemokines were detected by qRT-PCR in CCR9(-/-) mice. E. histolytica trophozoites were identified in the lumen of the cecum of CCR9(-/-) mice at seven days post infection (pi), whereas in CCR9(+/+) mice trophozoites disappeared by day 1 pi. Interestingly, the inflammation observed in CCR9(-/-) mice, was associated with a delayed recruitment of CD4(+)CD25(+)FoxP3(+) T cells to the cecal epithelium and lamina propria, suggesting that this population may play a role in the early regulation of the inflammatory response against E. histolytica, likely through IL-10 production. In support of these data, CCR9(+) T cells were also identified in colon tissue sections obtained from patients with amoebic colitis. Our data suggest that a population of CCR9(+)CD4(+)CD25(+)FoxP3(+) T cells may participate in the control and resolution of the inflammatory immune response to E. histolytica infection.

Trichinella spiralis: intranasal immunization with attenuated Salmonella enterica carrying a gp43 antigen-derived 30mer epitope elicits protection in BALB/c mice.

Trichinellosis is a public health problem and is considered an emergent/re-emergent disease in various countries. The etiological agent of trichinellosis is the nematode Trichinella, which infects domestic animals such as pigs and horses, as well as wild animals and humans. A veterinary vaccine could be an option to control the disease in domestic animals. Although several vaccine candidates have shown promising results, a vaccine against trichinellosis remains unavailable to date. Attenuated Salmonella strains are especially attractive live vectors because they elicit mucosal immunity, which is known to be important for the control of Trichinella spiralis infection at the intestinal level and can be administered by oral or intranasal routes. In this study, the autotransporter ShdA was used to display, on the surface of the Salmonella enterica serovar Typhimurium SL3261, the 210-239 amino acid epitope, (designated as Ag30) derived from the 43 kDa glycoprotein of T. spiralis muscle larvae. The fusion protein elicited antibodies in BALB/c mice that were able to recognize the native epitope on the surface of T. spiralis muscle larvae. Mice immunized by intranasal route with the recombinant Salmonella induced a protective immune response against the T. spiralis challenge, reducing by 61.83% the adult burden at day eight postinfection. This immune response was characterized by the induction of antigen-specific IgG1 and of IL-5 production. This study demonstrates the usefulness of Salmonella as a carrier of nematode epitopes providing a surface display system for intestinal parasite vaccine applications.

Proteolytic cleavage of chemokines by Trypanosoma cruzi's cruzipain inhibits chemokine functions by promoting the generation of antagonists.

Chagas disease is a chronic inflammatory disease caused by infection with Trypanosoma cruzi. Although it had a decline in recent years, it still affects millions of people in Latin America. The host immune response against this parasite is complex and relies on the development of an efficient T cell-mediated response; however, T. cruzi displays a number of evasion mechanisms allowing it to remain undetected even for years. One of these is the secretion of anti-inflammatory molecules such as proteases and the modulation of biological functions of chemokines. Our objective was to analyze the effect of a major cysteine protease, cruzipain, on a number of critical functions of several CC chemokines, both in vitro and in vivo. Initially, using a murine model of T. cruzi infection, we demonstrated that CCL-2 and CCL-12 chemokines are highly expressed at different stages and correlated with an increase in the expression of cruzipain. In addition, we demonstrated that cruzipain is capable of differentially cleaving CCL-2 and CCL-12 chemokines, as well as CCL-13. Analysis of the proteolysed products identified unique cleavage sites in these chemokines. These cruzipain-modified chemokine products were tested in chemotaxis assays using monocytic cells. We found that cruzipain treated-CCL-2 maintained its biological activity, in contrast to the closely related CCL-12 and CCL-13 chemokines, which showed little or null agonist activity after treatment. Furthermore, based on this analysis, a 14-mer cruzipain-derived chemokine peptide (CDCP-1) was chemically synthesized and tested for agonist activity using in vitro chemotaxis assays. Interestingly, CDCP-1 showed antagonist activity affecting in vitro migration of monocytic cells and calcium flux release. In conclusion, our results demonstrate that cruzipain modulates biological functions of chemokines through proteolytic cleavage, by generating chemokine-derived peptides with antagonist activities. This event could play a role during the latest phases of Chagas disease, when the parasite may differentially modulate chemokine-mediated inflammatory responses.

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.

Regulation of the inflammatory immune response by the cytokine/chemokine network in amoebiasis.

Amoebiasis is caused by the protozoa Entamoeba histolytica and persists as one of the leading parasitic diseases affecting millions worldwide. This parasite invades the intestinal mucosa, causing amoebic colitis and ulcers. It may also spread to other organs, mainly the liver, causing amoebic liver abscess (ALA). Current research efforts have focused on the development of specific diagnostic tests and animal models searching for a better understanding of the complex physiopathology of this disease. Analysis of the inflammatory immune response during intestinal amoebiasis in both human disease and animal murine models has revealed an important regulatory role for chemokines and cytokines. Recruitment and activation of inflammatory cells can also be modulated by specific protease-mediated cleavage of cytokines and by secreted amoebic factors such as amoebapores and monocyte locomotion inhibitory factor (MLIF). Unlike intestinal amoebiasis, analysis of the immune response in ALA has mainly been done in the hamster model. This has limited our information regarding the immune response during this phase of the disease. However, even with these limitations, several Th1/2 cytokines, such as IL-6 and IL-4, and regulatory cytokines, like IL-10 and TGFbeta, have been associated to the development of this disease.

IL-4 differentially regulates eotaxin and MCP-4 in lung epithelium and circulating mononuclear cells.

To investigate the mechanisms of eosinophil recruitment in allergic airway inflammation, we examined the effects of interleukin (IL)-4, a Th2-type cytokine, on eotaxin and monocyte chemoattractant protein-4 (MCP-4) expression in human peripheral blood mononuclear cells (PBMCs; n = 10), in human lower airway mononuclear cells (n = 5), in the human lung epithelial cell lines A549 and BEAS-2B, and in human cultured airway epithelial cells. IL-4 inhibited eotaxin and MCP-4 mRNA expression induced by IL-1 beta and tumor necrosis factor-alpha in PBMCs but did not significantly inhibit expression in epithelial cells. Eotaxin and MCP-4 mRNA expression was not significantly induced by proinflammatory cytokines in lower airway mononuclear cells. IL-1 beta-induced eotaxin and MCP-4 protein production was also inhibited by IL-4 in PBMCs, whereas IL-4 enhanced eotaxin protein production in A549 cells. In contrast, dexamethasone inhibited eotaxin and MCP-4 expression in both PBMCs and epithelial cells. The divergent effects of IL-4 on eotaxin and MCP-4 expression between PBMCs and epithelial cells may create chemokine concentration gradients between the subepithelial layer and the capillary spaces that may promote the recruitment of eosinophils to the airway in Th2-type responses.

Eotaxin expression after segmental allergen challenge in subjects with atopic asthma.

Expression of pulmonary eotaxin protein and mRNA was determined in six subjects with atopic asthma and five nonatopic normal subjects. Levels of eotaxin expression and eosinophil mobilization were compared before and after segmental allergen challenge in subjects with atopic asthma. In the absence of allergen challenge, we found significantly higher levels of eotaxin in the bronchoalveolar lavage (BAL) fluid of subjects with asthma than in that of normal subjects (25 +/- 3 versus 15 +/- 2 pg/ml, p < 0.05). BAL eotaxin levels increased after segmental allergen challenge in all six subjects with atopic asthma tested, with a mean increase from 22 +/- 4 to 53 +/- 10 pg/ml (p = 0.013). Segmental allergen challenge was associated with a significant increase in the percentage of BAL macrophages and eosinophils that were immunopositive for eotaxin. Eotaxin mRNA was detectable by northern analysis in BAL cells exclusively from allergen-challenged segments. Allergen- induced increases in eotaxin levels were strongly associated with increases in BAL eosinophil recovery (r(2) = 0.88, p = 0.0036). Segmental allergen challenge also increased eotaxin expression in airway epithelial and endothelial cells obtained by endobronchial biopsy. These findings demonstrate, for the first time, that the airways of subjects with allergic asthma respond to allergen by increasing eotaxin expression. The tissue loci of eotaxin expression, the levels of eotaxin recovered in BAL fluid, and the association of eotaxin levels with eosinophil mobilization suggest either that eotaxin plays a mechanistic role in allergen-induced airway eosinophilia or that it serves as a biomarker for the causal mechanisms.

Monocyte chemoattractant protein (MCP)-4 expression in the airways of patients with asthma. Induction in epithelial cells and mononuclear cells by proinflammatory cytokines.

Chemokines are chemotactic cytokines that play an important role in recruiting leukocytes in allergic inflammation. Monocyte chemoacctractant protein (MCP)-4 is a CC chemokine with potent chemotactic activities for eosinophils, monocytes, T lymphocytes, and basophils and therefore represents a good candidate to participate in allergic reactions. To determine if MCP-4 plays a role in asthma, we have investigated the expression of MCP-4 messenger RNA (mRNA) and protein in the airways of patients with asthma and normal control subjects by in situ hybridization and immunohistochemistry. We found that MCP-4 mRNA and protein was significantly upregulated in the epithelium and submucosa of bronchial biopsies and in the bronchoalveolar lavage (BAL) cells of patients with asthma compared with normal control subjects (p < 0. 01). In addition, MCP-4 protein was significantly elevated in the BAL fluid of patients with atopic asthma when compared with normal control subjects (p < 0.01) and there was a significant correlation between MCP-4, eotaxin, and eosinophils. In support of our in situ findings demonstrating MCP-4 expression in epithelial cells and mononuclear cells in vivo, we have found that MCP-4 expression can be induced in these cells in vitro by tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta). Interferon-gamma (IFN-gamma) acted synergistically with TNF-alpha and IL-1beta in the induction of mRNA MCP-4 mRNA expression in A549 cells, whereas the glucocorticoid dexamethasone diminished the cytokine-induced expression of MCP-4. Our findings demonstrate that MCP-4 is upregulated in the airways of patients with asthma and suggest that MCP-4 plays a role in the recruitment of eosinophils into the airways of patients with asthma.

C-C and C-X-C chemokines trigger firm adhesion of monocytes to vascular endothelium under flow conditions.

In summary, our findings indicate that specific chemokines that are elaborated by endothelial cells after cytokine or endotoxin activation can play an essential role in monocyte recruitment beyond their chemoattractant activities. We show that this action is to translate initial monocyte tethering into firm adhesion via rapid leukocyte integrin activation. The in vitro model presented here provides a sensitive system for investigating the modulating ability of chemokines and reveals an important biological effect that is not predicted by results in simpler in vitro assays, such as measurement of calcium transients or chemotaxis. The surprising finding that the C-X-C chemokine IL-8 can trigger monocyte firm adhesion to vascular endothelium suggests a potential role for this chemokine in monocyte recruitment and underscores the biological complexity of the chemokine family.

MCP-1 and IL-8 trigger firm adhesion of monocytes to vascular endothelium under flow conditions.

Monocytes contribute to the development of atherosclerotic lesions in mouse models. The chemoattractant proteins (chemokines), monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8), are found in human atheroma, and mice lacking receptors for these chemokines are less susceptible to atherosclerosis and have fewer monocytes in vascular lesions. Although MCP-1 has a powerful effect on monocytes, IL-8 is thought to act predominantly on neutrophils and it is unclear how it could recruit monocytes. Here we investigate the ability of chemokines to control the interaction of monocytes under flow conditions with vascular endothelium that has been transduced to express specific leukocyte-adherence receptors. We find that MCP-1 and IL-8 can each rapidly cause rolling monocytes to adhere firmly onto monolayers expressing E-selectin, whereas related chemokines do not. These effects do not correlate with either the induction of a calcium transient or chemotaxis. We conclude that chemokines are important modulators of monocyte-endothelial interactions under flow conditions. Moreover, our finding that IL-8 is a powerful trigger for firm adhesion of monocytes to vascular endothelium reveals an unexpected role for this chemokine in monocyte recruitment.

The T cell-specific CXC chemokines IP-10, Mig, and I-TAC are expressed by activated human bronchial epithelial cells.

Recruitment of activated T cells to mucosal surfaces, such as the airway epithelium, is important in host defense and for the development of inflammatory diseases at these sites. We therefore asked whether the CXC chemokines IFN-induced protein of 10 kDa (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha-chemoattractant (I-TAC), which specifically chemoattract activated T cells by signaling through the chemokine receptor CXCR3, were inducible in respiratory epithelial cells. The effects of proinflammatory cytokines, including IFN-gamma (Th1-type cytokine), Th2-type cytokines (IL-4, IL-10, and IL-13), and dexamethasone were studied in normal human bronchial epithelial cells (NHBEC) and in two human respiratory epithelial cell lines, A549 and BEAS-2B. We found that IFN-gamma, but not TNF-alpha or IL-1 beta, strongly induced IP-10, Mig, and I-TAC mRNA accumulation mainly in NHBEC and that TNF-alpha and IL-1 beta synergized with IFN-gamma induction in all three cell types. High levels of IP-10 protein (> 800 ng/ml) were detected in supernatants of IFN-gamma/TNF-alpha-stimulated NHBEC. Neither dexamethasone nor Th2 cytokines modulated IP-10, Mig, or I-TAC expression. Since IFN-gamma is up-regulated in tuberculosis (TB), using in situ hybridization we studied the expression of IP-10 in the airways of TB patients and found that IP-10 mRNA was expressed in the bronchial epithelium. In addition, IP-10-positive cells obtained by bronchoalveolar lavage were significantly increased in TB patients compared with normal controls. These results show that activated bronchial epithelium is an important source of IP-10, Mig, and I-TAC, which may, in pulmonary diseases such as TB (in which IFN-gamma is highly expressed) play an important role in the recruitment of activated T cells.

Molecular and biological characterization of the murine leukotriene B4 receptor expressed on eosinophils.

The movement of leukocytes into tissues is regulated by the local production of chemical mediators collectively referred to as chemoattractants. Although chemoattractants constitute a diverse array of molecules, including proteins, peptides, and lipids, they all appear to signal leukocytes through a related family of seven transmembrane-spanning G protein-coupled receptors. The eosinophil is a potent proinflammatory cell that is attracted into tissues during allergic inflammation, parasitic infection, and certain malignancies. Since the molecular mechanisms controlling eosinophil recruitment are incompletely understood, we performed a degenerate polymerase chain reaction on cDNA isolated from murine eosinophils to identify novel chemoattractant receptors. We report the isolation of a cDNA that encodes a 351-amino acid glycoprotein that is 78% identical to a human gene that has been reported to be a purinoceptor (P2Y7) and a leukotriene B4 (LTB4) receptor (BLTR). Chinese hamster ovary (CHO) cells transfected with this cDNA specifically bound [3H]LTB4 with a dissociation constant of 0.6 +/- 0.1 nM. Furthermore, LTB4 induced a dose-dependent intracellular calcium flux in transfected CHO cells. In contrast, [35S]dATP did not specifically bind to these transfectants. This mRNA was expressed at high levels in interleukin 5-exposed eosinophils, elicited peritoneal macrophages and neutrophils, and to a lesser extent interferon gamma stimulated macrophages. Low levels of expression were detected in the lung, lymph node, and spleen of unchallenged mice. Western blot analysis detected the mBLTR protein in murine eosinophils and alveolar macrophages as well as human eosinophils. In addition, elevated levels of mBLTR mRNA were found in the lungs of mice in a murine model of allergic pulmonary inflammation in a time course consistent with the influx of eosinophils. Our findings indicate that this murine receptor is an LTB4 receptor that is highly expressed on activated leukocytes, including eosinophils, and may play an important role in mediating eosinophil recruitment into inflammatory foci.

Beta-chemokines are released from HIV-1-specific cytolytic T-cell granules complexed to proteoglycans.

CD8+ lymphocytes are believed to be important in host defence against the human immunodeficiency virus (HIV)-1, inhibiting HIV-1 replication through both cytolytic and non-cytolytic pathways. The cytolytic pathway involves calcium-dependent exocytosis of perforin and granzyme proteases, as well as Fas-mediated programmed cell death, whereas the noncytolytic pathway involves the release of chemokines that prevent viral entry. Using granzyme A as a marker of cytolytic granule proteins, and macrophage inflammatory protein (MIP)-1alpha and RANTES as markers of HIV-1 inhibitory chemokines, we show that these two very different mediators of viral inhibition are both localized in the cytolytic granules of HIV-1-specific CD8+ cytotoxic T lymphocytes (CTL). Following antigen-specific activation, these mediators are secreted together, facilitating both lysis of virion-producing cells and the inhibition of free virus. In addition, RANTES, MIP-1alpha and MIP-1beta are secreted by CTL as a macromolecular complex containing sulphated proteoglycans. This association appears to have a functional significance, because heparan sulphate facilitates RANTES inhibition of HIV-1 infection of monocytes.

Human immunodeficiency virus-1 entry into purified blood dendritic cells through CC and CXC chemokine coreceptors.

Blood dendritic cells (DC) are susceptible to both macrophage (M) and T-cell line (T) tropic human immunodeficiency virus type 1. The CC chemokines RANTES, macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, eotaxin, and, to a lesser extent, monocyte chemoattractant protein-1 (MCP-1) and MCP-4 blocked entry of M-tropic virus into blood DC. The CXC chemokine, SDF-1, a fusin (CXCR4 chemokine receptor) ligand, and an antifusin antibody inhibited DC entry by T-tropic virus. Purified blood DC contained CCR1, CCR2, CCR3, and CCR5 as well as the CXCR4 chemokine receptor RNA transcripts and high levels of fusin on the cell surface. The coexpression of multiple chemokine receptors offers a molecular mechanism to explain the permissiveness of DC for both M- and T-tropic viruses.

Genomic organization, complete sequence, and chromosomal location of the gene for human eotaxin (SCYA11), an eosinophil-specific CC chemokine.

Eotaxin is a CC chemokine that is a specific chemoattractant for eosinophils and is implicated in the pathogenesis of eosinophilic inflammatory diseases, such as asthma. We describe the genomic organization, complete sequence, including 1354 bp 5' of the RNA initiation site, and chromosomal localization of the human eotaxin gene. Fluorescence in situ hybridization analysis localized eotaxin to human chromosome 17, in the region q21.1-q21.2, and the human gene name SCYA11 was assigned. We also present the 5' flanking sequence of the mouse eotaxin gene and have identified several regulatory elements that are conserved between the murine and the human promoters. In particular, the presence of elements such as NF-kappa B, interferon-gamma response element, and glucocorticoid response element may explain the observed regulation of the eotaxin gene by cytokines and glucocorticoids.

Expression of eotaxin by human lung epithelial cells: induction by cytokines and inhibition by glucocorticoids.

Eotaxin is a potent and specific eosinophil chemoattractant that is mobilized in the respiratory epithelium after allergic stimulation. Pulmonary levels of eotaxin mRNA are known to increase after allergen exposure in sensitized animals. In this study we demonstrate that TNF alpha and IL-1beta induce the accumulation of eotaxin mRNA in the pulmonary epithelial cell lines A549 and BEAS 2B in a dose-dependent manner. Cytokine-induced A549 cell mRNA accumulation was maximal at 4 h and was significantly enhanced when the cells were costimulated with IFNgamma. TNFalpha- and IL-1beta-induced increases in eotaxin mRNA were diminished in a dose-dependent manner by the glucocorticoid dexamethasone and were augmented by the protein synthesis inhibitor cycloheximide. Cytokine-induced increases in eotaxin mRNA expression correlated with increased eotaxin protein production and secretion, and dexamethasone inhibition of cytokine-induced eotaxin mRNA augmentation was associated with diminished eotaxin protein secretion. These findings, together with the known kinetics of TNF alpha and IL-1beta mobilization in asthmatic airways and the potent eosinophil chemotactic effects of eotaxin, define a mechanism linking inflammatory cytokine mobilization to eosinophil recruitment that may be relevant to the pathogenesis of asthma.