Macrophage-derived Chemokine Is a Functional Ligand for the CC Chemokine Receptor 4

TARC/CCL17 (thymus- and activation-regulated chemokine) is a CC chemokine, which binds to the CC chemokine receptor-4 (CCR4) known to be distinctively expressed on Th2 lymphocytes. In atopic dermatitis (AD), the skin is invaded by Th2 lymphocytes in the acute phase. TARC/CCL17 is produced by the keratinocytes in AD lesions, and CCR4 is overexpressed on CLA+ (cutaneous lymphocyte-associated antigen) lymphocytes in the skin and blood. We, therefore, hypothesized that TARC/CCL17 is pivotal in mediating a Th2-dominated inflammation in the skin. To examine this, we injected BALB/c mice with murine TARC/CCL17 in concentrations ranging from 0.1 microg/ml to 10 microg/ml and examined the skin after 48 h. This revealed that TARC/CCL17 induces lymphocytic infiltration of the skin by CD4+ lymphocytes in a dose-dependent manner with a maximum response at 1 microg/ml. Additionally, TARC/CCL17 induced interleukin-4 mRNA but not interferon-gamma mRNA expression in the skin, suggesting that the lymphocytes invading the skin are Th2 cells. Additionally, TARC/CCL17 induced its own production in the keratinocytes along with cutaneous T-cell-attracting chemokine (CTACK/CCL27) mRNA. We, therefore, conclude that TARC/CCL17 induces a Th2-dominated inflammatory reaction when injected into the skin.

Chemokines are a large superfamily of approximately 50 peptides. Although they are involved in diverse processes, their central and defining role in mammals appears to be action toward subpopulations of leukocytes (1). This specificity is mediated by selective expression of chemokine receptors, heptahelical G-protein coupled membrane molecules. With time and further study, chemokines have now been implicated in developmental organogenesis, angiogenesis, neoplasia, differentiation, and a host of other physiological and pathological processes (2, 3). Considerable interest has been sparked by the discovery that several chemokine receptors are essential invasion coreceptors for human immunodeficiency virus (HIV)-1 and HIV-2 infection of human cells (4, 5).

Chemokine G-protein coupled receptors are validated drug targets for many diseases, including cancer, neurological, and inflammatory disorders. Despite much time and effort spent on therapeutic development, very few chemokine receptor antagonists are approved for clinical use. Among potential reasons for the slow progress in developing chemokine receptor inhibitors, antagonist tolerance, a progressive reduction in drug efficacy after repeated administration, is likely to play a key role. The mechanisms leading to antagonist tolerance remain poorly understood. In many cases, antagonist tolerance is accompanied by increased receptor concentration on the cell surface after prolonged exposure to chemokine receptor antagonists. This points to a possible role of altered receptor internalization and presentation on the cell surface, as has been shown for agonist (primarily opioid) tolerance. In addition, examples of antagonist tolerance in the context of other G-protein coupled receptors suggest the involvement of noncanonical signal transduction in opposing the effects of the antagonists. In this review, we summarize the available progress and challenges in therapeutic development of chemokine receptor antagonists, describe the available knowledge about antagonist tolerance, and propose new avenues for future investigation of this important phenomenon. Furthermore, we highlight the modern methodologies that have the potential to reveal novel mechanisms leading to antagonist tolerance and to propel the field forward by advancing the development of potent “tolerance-free” antagonists of chemokine receptors.

Today, 10 years after the discovery of IL-8, chemokines (chemotactic cytokines) are seen as the stimuli that largely control leucocyte migration. Chemokines are low molecular weight chemoattractant cytokines secreted by a variety of cells, including leucocytes, epithelial cells, endothelial cells, fibroblasts and numerous other cell types. They are produced in response to exogenous stimuli, such as viruses and bacterial LPS, and endogenous stimuli, such as IL-1, TNF and IFN. These factors mediate chemotaxis and leucocyte activation. They also regulate leucocyte extravasation from the blood and/or lymph vessel luminal surface to the tissue space, the site of inflammation. There is no doubt that chemokines and chemokine receptors are critical for defence against infectious pathogens. It is also clear that these pathogens have evolved to accommodate the workings of the host immune system. Survival of these infectious agents appears dependent upon strategies that can evade, suppress, counteract or otherwise confound the constellation of host responses to invading pathogens. In this regard, the chemokines and their receptors are a major target. Reviewed in the present paper are several examples in which microbial pathogens have usurped the mammalian chemokine system to subvert the host immune response.

In the present study we investigated the effect of SCF and/or IgE on histamine, TNF-alpha and chemokines released from bone marrow-derived mast cells (BMMC) as well as chemokine receptor expression. BMMC were derived from femoral bone marrow of CBA/J mice. The purity of BMMC was >98% after 3 weeks. BMMC (2.5 x 10(6) cells/well) were incubated in the presence or absence of either SCF, IgE plus DNP or a combination of SCF and IgE for 6 and 18 h. Cell-free supernatants were recovered to measure CC chemokines, TNF-alpha and histamine release utilizing ELISA assays. CC chemokine family receptors were detected by RT-PCR analysis, and confirmed using functional chemotactic assays. Histamine levels were comparable between SCF and IgE stimulated cells, whereas TNF-alpha production was significantly greater after IgE compared to SCF stimulation. SCF and/or IgE-stimulated BMMC released CC chemokines, CCL22 (MDC), CCL17 (TARC) and CCL2 (MCP-1). Increased mRNA expression of CCR1, CCR2, CCR3, and CCR5 was detected in SCF and IgE-stimulated BMMCs. Functional chemotactic assays confirmed the expression data. SCF and IgE can up-regulate the expression of chemokines and chemokine receptors on mast cells. Thus, SCF may play a significant role in their activation and inflammation during allergic responses.

Mononuclear Cell-Infiltrate Inhibition by Blocking Macrophage-Derived Chemokine Results in Attenuation of Developing Crescentic Glomerulonephritis

BackgroundPrevious studies have indicated that C-C class chemokine ligand 22 (CCL22) is involved in the pathogenesis of tuberculous pleural effusion and malignant pleural effusion. However, the diagnostic role of pleural fluid CCL22 levels in patients with undiagnosed pleural effusions remains to be elucidated.MethodsWe prospectively recruited patients with undiagnosed pleural effusion who visited two centres (Hohhot and Changshu) in China. Pleural biopsy, microbiological culture and effusion cytology were used to verify the cause of pleural effusion. Pleural fluid CCL22 levels were measured using an ELISA. The diagnostic accuracy of CCL22 for identifying heart failure (HF) was evaluated using a receiver operating characteristic (ROC) curve, and the net benefit of CCL22 was evaluated using decision curve analysis (DCA). Net benefit was defined as the benefit associated with true positives minus the harms associated with false positives at various threshold probabilities.ResultsWe enrolled 153 and 58 patients in the Hohhot and Changshu cohorts, respectively. The cohort included 28 patients with HF and 183 patients with non-HF. Patients with HF had significantly lower pleural fluid CCL22 levels than non-HF patients. The area under the ROC curve (AUC) of CCL22 was 0.85 (95% CI: 0.77 to 0.93) in the Hohhot cohort and 0.87 (95% CI: 0.75 to 0.98) in the Changshu cohort. The AUC in the combined cohort was 0.85 (95% CI: 0.79 to 0.92), with a sensitivity of 0.82 (95% CI: 0.68 to 0.93) and a specificity of 0.73 (95% CI: 0.67 to 0.79) at the threshold of 150 ng/mL. DCA revealed a potential net benefit of pleural CCL22 determination in patients with undiagnosed pleural effusions.ConclusionsPleural fluid CCL22 may be a potential diagnostic marker for HF-related pleural effusion. Owing to the small sample size of this study, further studies with larger sample sizes are needed to validate our findings.

Potent and orally bioavailable CCR4 antagonists: Synthesis and structure–activity relationship study of 2-aminoquinazolines

Increase in Activated Treg in TIL in Lung Cancer and In Vitro Depletion of Treg by ADCC Using an Antihuman CCR4 mAb (KM2760)

Th2 cells are thought to be involved in eosinophilic inflammation of the lung. CC chemokine receptor 4 (CCR4) has been identified as a specific receptor for both thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC), and is preferentially expressed on Th2 cells. Our aim was to evaluate the role of Th2 cells in the lung of patients with eosinophilic pneumonia (EP). The concentrations of TARC, MDC, and interleukin (IL)-5 were measured in bronchoalveolar lavage fluid (BALF) by ELISA. Proportion of CCR4-expressing CD4+ T cells (CCR4+ CD4+ T cells) was determined by flow cytometry. TARC and MDC concentrations in BALF were higher in patients with EP than in normal subjects. The proportion of CCR4-expressing cells among CD4+ T cells was higher in BALF than in peripheral blood of patients with EP. There was a significant correlation between the number of CCR4+ CD4+ T cells and the levels of TARC, MDC, and IL-5 in BALF of patients with EP. Our data suggest that Th2 cells, which express CCR4 and its ligands (TARC and MDC), contribute to the pathogenesis of EP in the lung.