Chemokine Scavenger Receptor D6 Research Articles

The chemokine scavenging receptor D6/ACKR2 is a target of miR-146a in thyroid cancer

We have previously shown that miR-146a, a NF-κB-regulated microRNA, is strongly expressed in human specimens and cell lines derived from anaplastic thyroid carcinomas (ATC) where it mediates some of the NF-κB pro-tumorigenic functions. By using a bioinformatic analysis, we identified the chemokine scavenger receptor D6/ ACKR2 as a target of miR146a in human ATC. We found that the expression of D6/ ACKR2 was up-regulated in miR-146a-null ATC cell lines and that the 3’ UTR of D6/ ACKR2 mRNA was able to inhibit its expression in parental, but not in miR-146a-null ATC cells. Since human specimens from primary ATC showed a low expression of D6/ ACKR2 compared to normal thyroid tissues, we analyzed the effects of D6/ACKR2 over-expression in ATC cells. Different chemokines added to the conditioned medium of D6/ACKR2 over-expressing ATC cells partially failed to drive in vitro monocyte migration, and tumors derived from the injection of the same cells in nude mice showed a decreased number of infiltrating macrophages.Taken together, these results indicate that ATC cells down-regulate D6/ACKR2 expression through miR-146a activity to sustain leukocyte trafficking inside tumor microenvironment and shed light on a novel mechanism by which NF-κB indirectly inhibits the expression and the function of anti-tumorigenic gene in thyroid cancer.

Regulation of expression of the chemokine-scavenging receptor D6 by microRNAs

Regulation of expression of the chemokine-scavenging receptor D6 by microRNAs

Increased number and altered phenotype of lymphatic vessels in peripheral lung compartments of patients with COPD

BackgroundDe novo lymphatic vessel formation has recently been observed in lungs of patients with moderate chronic obstructive pulmonary disease (COPD). However, the distribution of lymphatic vessel changes among the anatomical compartments of diseased lungs is unknown. Furthermore, information regarding the nature of lymphatic vessel alterations across different stages of COPD is missing. This study performs a detailed morphometric characterization of lymphatic vessels in major peripheral lung compartments of patients with different severities of COPD and investigates the lymphatic expression of molecules involved in immune cell trafficking.MethodsPeripheral lung resection samples obtained from patients with mild (GOLD stage I), moderate-severe (GOLD stage II-III), and very severe (GOLD stage IV) COPD were investigated for podoplanin-immunopositive lymphatic vessels in distinct peripheral lung compartments: bronchioles, pulmonary blood vessels and alveolar walls. Control subjects with normal lung function were divided into never smokers and smokers. Lymphatics were analysed by multiple morphological parameters, as well as for their expression of CCL21 and the chemokine scavenger receptor D6.ResultsThe number of lymphatics increased by 133% in the alveolar parenchyma in patients with advanced COPD compared with never-smoking controls (p < 0.05). In patchy fibrotic lesions the number of alveolar lymphatics increased 20-fold from non-fibrotic parenchyma in the same COPD patients. The absolute number of lymphatics per bronchiole and artery was increased in advanced COPD, but numbers were not different after normalization to tissue area. Increased numbers of CCL21- and D6-positive lymphatics were observed in the alveolar parenchyma in advanced COPD compared with controls (p < 0.01). Lymphatic vessels also displayed increased mean levels of immunoreactivity for CCL21 in the wall of bronchioles (p < 0.01) and bronchiole-associated arteries (p < 0.05), as well as the alveolar parenchyma (p < 0.001) in patients with advanced COPD compared with never-smoking controls. A similar increase in lymphatic D6 immunoreactivity was observed in bronchioles (p < 0.05) and alveolar parenchyma (p < 0.01).ConclusionsThis study shows that severe stages of COPD is associated with increased numbers of alveolar lymphatic vessels and a change in lymphatic vessel phenotype in major peripheral lung compartments. This novel histopathological feature is suggested to have important implications for distal lung immune cell traffic in advanced COPD.

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

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

Satiated-efferocytosis: A novel functional property for resolution-phase macrophages regulated by glucocorticoids, resolvins, galectin-1 and the chemokine-scavenging receptor D6 (P4157)

Abstract The engulfment of apoptotic leukocytes (efferocytosis) by macrophages during the resolution of inflammation is essential for homeostasis and results in macrophage reprogramming/immune-silencing. Here, we show CD11bhigh macrophages convert to CD11blow ones and stop efferocytosing apoptotic PMN after reaching an engulfment threshold in vivo. In addition, CD11blow macrophages are distinct from either M1 or M2 in their protein expression profile and display pro-resolving properties, such as diminished responses to different TLR ligands ex vivo and propensity to emigrate from resolving inflammation sites to lymphoid organs. Of interest, we found the pro-resolving lipid mediators resolvin E1 and D1, as well as the glucocorticoid dexamethasone (Dex) and the lectin galectin-1 enhance satiated-efferocytosis and consequently CD11blow macrophage conversion from their CD11bhigh counterparts. Deficiency in the atypical chemokine receptor D6 resulted in delayed satiation and reduced immune-silencing of macrophages, and inhibits their departure from resolving inflammation sites. In sum, satiated-efferocytosis is a novel phagocyte property of CD11blow macrophages that is regulated by pro-resolving mediators. Moreover, satiated-efferocytosis is required for CD11blow macrophage emigration from resolving inflammation sites and the return of tissue homeostasis. Thus, satiated-efferocytosis is essential for the completion of timely- and spatially-coordinated resolution of acute inflammation.

P041 G protein-independent signalling by the chemokine scavenger receptor D6 is required for its chemokine scavenging activity

Introduction Chemokine receptors include a set of molecules referred to as “atypical” chemokine receptors (ACR) because unable to induce directional cell migration and elicit conventional GPCR signalling. As no signaling activity has been observed after ACR engagement by their ligands, they are presently considered “silent” receptors. D6 is an ACR with scavenger activity on inflammatory CC chemokines with a non-redundant role for appropriate regulation of innate immunity and inflammation. Methods D6 expression was evaluated by FACS and confocal microscopy. Chemokine degradation was measured by ELISA test. Protein phosphorylation levels were detected by western blot. Results Our previous data showed that, differently from CCR5, ligand induces D6 up-regulation on plasma membrane through a rapid mobilization of receptor from recycling endosomes, thus improving its scavenging performance. Here we report that in cells expressing D6 or CCR5, ligand engagement causes a massive actin cytoskeleton reorganization and changes receptors colocalization with actin filaments in a completely opposite fashion. Both receptors signal to actin cytoskeleton by phosphorylating cofilinA through the Rac1-PAK1-LIMK1-dependent pathway. However, opposite to CCR5, D6 activates this pathway via a beta-arrestin-dependent, G protein-independent mechanism. Inhibition of each component of this signaling cascade completely abrogates D6 adaptive upregulation and scavenging activity. Conclusion D6, and possibly ACR in general, are signaling receptors exerting their regulatory functions on inflammation and immunity via the activation of a distinct signaling pathway.

Adaptive immunity suppresses formation and progression of diethylnitrosamine-induced liver cancer

BackgroundHepatocellular carcinoma (HCC) is a typical inflammation-associated cancer, but may also provoke antitumour immune responses whose significance and underlying mechanisms are incompletely understood.ObjectiveTo characterise immune responses in the diethylnitrosamine (DEN)-liver...

The chemokine scavenging receptor D6 limits acute toxic liver injury in vivo

The chemokine decoy receptor D6 is a promiscuous chemokine receptor lacking classical signaling functions. It negatively regulates inflammation by targeting CC chemokines to cellular internalization and degradation. Here we analyze the function of D6 in acute CCl(4)-induced liver damage in constitutive D6(-/-) and wild-type mice. The degree of liver injury was assessed by liver histology, serum transaminases, IL-6, and TNFalpha mRNA expression. Protein levels of D6 ligands (CCL2, CCL3, CCL5) and the non-D6-ligand CXCL9 within the livers were determined by ELISAs. The intrahepatic infiltration of immune cells was characterized by FACS. Genetic deletion of D6 led to prolonged liver damage after acute CCl(4) administration. The augmented liver damage in D6(-/-) mice was associated with increased protein levels of intrahepatic inflammatory chemokines CCL2, CCL3, and CCL5 after 48 h, whereas CXCL9 was not different between knockout and wild-type mice. Functionally, increased intra-hepatic CC chemokine concentrations led to increased infiltration of CD45(+) leukocytes, which were mainly identified as T and NK cells. In conclusion, the chemokine scavenger receptor D6 has a non-redundant role in acute toxic liver injury in vivo. These results support the importance of post-translational chemokine regulation and describe a new mechanism of immune modulation within the liver.

Genetic variations of the chemokine scavenger receptor D6 are associated with liver inflammation in chronic hepatitis C

Chronic hepatitis C (HCV) represents one of the most common chronic infections worldwide and is a major indication for liver transplantation. Liver inflammation is the main predictor of advanced fibrosis in HCV. Inflammatory cells are recruited to the liver by chemokines. Recently, a novel class of chemokine receptors has been characterized that lack signaling functions and are termed scavenger receptors. We determine here whether genetic variations of the scavenger receptor D6 contribute to the grade of liver inflammation in HCV. Four haplotype tagging single nucleotide polymorphisms (SNPs) were identified from HapMap that cover the genetic information of D6 ( CCBP2). Among these SNPs, rs4683336 was associated with liver inflammation in qualitative ( p = 0.003) and quantitative ( p = 0.0086) genotype analysis. This association was confirmed in an independent cohort of HCV-infected patients ( p = 0.006 for qualitative and p = 0.0046 for quantitative analysis, respectively). Furthermore, the haplotype that is tagged by marker rs4683336 was significantly correlated with liver inflammation when compared with the most common D6 haplotype ( p = 0.014). The importance of genetic variations in D6 was supported through the demonstration of an association of D6 mRNA expression with histologic inflammation in liver biopsies and a considerable range of D6 mRNA expression in isolated human hepatocytes. In conclusion, we demonstrate that variations in a chemokine scavenging receptor are significantly correlated with clinical inflammatory phenotypes such as HCV infection.

A Novel Mechanism for CCR4 in the Regulation of Macrophage Activation in Bleomycin-Induced Pulmonary Fibrosis

Macrophage polarization into M1 or M2 phenotypes dictates the nature, duration, and severity of an inflammatory response. The objective of this study was to examine the role of CC chemokine receptor 4 (CCR4) in macrophage polarization during pulmonary oxidative injury in wild-type [WT (CCR4(+/+))] and CCR4-deficient (CCR4(-/-)) mice. Intrapulmonary administration of bleomycin sulfate provoked lethal inflammatory and fibrotic responses in WT (CCR4(+/+)) mice, but such responses were absent in CCR4(-/-) mice. Transcript and protein analyses of alveolar and bone marrow-derived macrophages showed that cells isolated from CCR4(-/-) mice did not exhibit CCL17-dependent M1 activation in response to bleomycin. Instead, CCR4(-/-) macrophages showed an M2 phenotype characterized by significantly elevated expression of arginase 1 and FIZZ1 (found in inflammatory zone 1), particularly during the peak of pulmonary inflammation. Compared with WT (CCR4(+/+)) mice, CCR4(-/-) mice exhibited a significant increase in the expression of the nonsignaling CC chemokine scavenging receptor D6 in whole lung samples and isolated macrophages. Thus, these results demonstrate that CCL17-dependent activation of CCR4 in macrophages plays a central role in free radical-induced pulmonary injury and repair.