Human CC chemokine liver-expressed chemokine/CCL16 is a functional ligand for CCR1, CCR2 and CCR5, and constitutively expressed by hepatocytes

A list of candidate cancer biomarkers for targeted proteomics

We have compiled from literature and other sources a list of 1261 proteins believed to be differentially expressed in human cancer. These proteins, only some of which have been detected in plasma to date, represent a population of candidate plasma biomarkers that could be useful in early cancer detection and monitoring given sufficiently sensitive specific assays. We have begun to prioritize these markers for future validation by frequency of literature citations, both total and as a function of time. The candidates include proteins involved in oncogenesis, angiogenesis, development, differentiation, proliferation, apoptosis, hematopoiesis, immune and hormonal responses, cell signaling, nucleotide function, hydrolysis, cellular homing, cell cycle and structure, the acute phase response and hormonal control. Many have been detected in studies of tissue or nuclear components; nevertheless we hypothesize that most if not all should be present in plasma at some level. Of the 1261 candidates only 9 have been approved as "tumor associated antigens" by the FDA. We propose that systematic collection and large-scale validation of candidate biomarkers would fill the gap currently existing between basic research and clinical use of advanced diagnostics.

Structure/Function Relationships of CCR8 Agonists and Antagonists

We describe here the interactions of CCR8 with its ligands using both CCR8 transfectants and a T-cell line expressing the receptor endogenously. Of the CCR8 agonists reported previously, only CCL1 and vMIP-I exhibited potency in assays of intracellular calcium flux, chemotaxis, and receptor internalization, this latter mechanism being dependent upon the expression of beta-arrestins 1 and 2 but independent of Galpha(i) signaling. NH(2)-terminal extension of the mature CCL1 sequence by a serine residue (Ser-CCL1) resulted in a partial agonist with a reduced affinity for CCR8, suggesting that the NH(2) terminus of the ligand plays a role in ligand binding to an intrahelical site. Attempts to identify key residues within this site revealed that the conserved glutamic acid residue in transmembrane helix 7, Glu-286, is crucial for trafficking of the receptor to the cell surface, while Asp-97 of transmembrane helix 2 is dispensable. CCL7 was found to inhibit both Ser-CCL1 and vMIP-I responses but not those of CCL1 itself. Similarly, vMIP-I responses were more than 2 orders of magnitude more sensitive to the specific CCR8 antagonist MC148 than those induced by CCL1, which is difficult to reconcile with the reported affinities for the receptor. Collectively, these data suggest that the CCR8 ligands are allotropic, binding to distinct sites within CCR8 and that the human immune system may have evolved to use CCL7 as a selective antagonist of viral chemokine activity at CCR8 but not those of the host ligand.

The Human Specific CCR1 Antagonist CP-481,715 Inhibits Cell Infiltration and Inflammatory Responses in Human CCR1 Transgenic Mice

We previously described the in vitro characteristics of the potent and selective CCR1 antagonist, CP-481,715. In addition to being selective for CCR1 vs other chemokine receptors, CP-481,715 is also specific for human CCR1 (hCCR1), preventing its evaluation in classical animal models. To address this, we generated mice whereby murine CCR1 was replaced by hCCR1 (knockin) and used these animals to assess the anti-inflammatory properties of CP-481,715. Cells isolated from hCCR1 knockin mice were shown to express hCCR1 and migrate in response to both murine CCR1 and hCCR1 ligands. Furthermore, this migration is inhibited by CP-481,715 at dose levels comparable to those obtained with human cells. In animal models of cell infiltration, CP-481,715 inhibited CCL3-induced neutrophil infiltration into skin or into an air pouch with an ED50 of 0.2 mg/kg. CP-481,715 did not inhibit cell infiltration in wild-type animals expressing murine CCR1. In a more generalized model of inflammation, delayed-type hypersensitivity, CP-481,715 significantly inhibited footpad swelling and decreased the amount of IFN-gamma and IL-2 produced by isolated spleen cells from sensitized animals. It did not, however, induce tolerance to a subsequent challenge. These studies illustrate the utility of hCCR1 knockin animals to assess the activity of human specific CCR1 antagonists; demonstrate the ability of the CCR1 antagonist CP-481,715 to inhibit cell infiltration, inflammation, and Th1 cytokine responses in these animals; and suggest that CP-481,715 may be useful to modulate inflammatory responses in human disease.

Quantum proteolytic activation of chemokine CCL15 by neutrophil granulocytes modulates mononuclear cell adhesiveness

Monocyte infiltration into inflammatory sites is generally preceded by neutrophils. We show here that neutrophils may support this process by activation of CCL15, a human chemokine circulating in blood plasma. Neutrophils were found to release CCL15 proteolytic activity in the course of hemofiltration of blood from renal insufficiency patients. Processing of CCL15 immunoreactivity (IR) in the pericellular space is suggested by a lack of proteolytic activity in blood and blood filtrate, but a shift of the retention time (t(R)) of CCL15-IR, detected by chromatographic separation of CCL15-IR in blood and hemofiltrate. CCL15 molecules with N-terminal deletions of 23 (delta23) and 26 (delta26) aa were identified as main proteolytic products in hemofiltrate. Neutrophil cathepsin G was identified as the principal protease to produce delta23 and delta26 CCL15. Also, elastase displays CCL15 proteolytic activity and produces a delta21 isoform. Compared with full-length CCL15, delta23 and delta26 isoforms displayed a significantly increased potency to induce calcium fluxes and chemotactic activity on monocytes and to induce adhesiveness of mononuclear cells to fibronectin. Thus, our findings indicate that activation of monocytes by neutrophils is at least in part induced by quantum proteolytic processing of circulating or endothelium-bound CCL15 by neutrophil cathepsin G.

Differential CCR1-mediated chemotaxis signaling induced by human CC chemokine HCC-4/CCL16 in HOS cells

Human CC chemokine-4 (HCC-4)/CCL16 is a chemoattractant for monocytes and lymphocytes. Although HCC-4 binds to multiple CC chemokine receptors, the receptor-mediated signal transduction pathway induced by HCC-4 has not been characterized. Human osteogenic sarcoma cells stably expressing CCR1 were used to investigate HCC-4-mediated chemotaxis signaling events via CCR1. The chemotactic activity of HCC-4 as well as those of other CCR1-dependent chemokines including MIP-1alpha/CCL3, RANTES/CCL5, and Lkn-1/CCL15 was inhibited by the treatment of pertussis toxin, an inhibitor of Gi/Go protein, U73122, an inhibitor of phospholipase C (PLC), and rottlerin, a specific inhibitor of protein kinase Cdelta (PKCdelta). These results indicate that HCC-4-induced chemotaxis signaling is mediated through Gi/Go protein, PLC, and PKCdelta. SB202190, an inhibitor of p38 mitogen activated protein kinase, only blocked the chemotactic activity of HCC-4, but not those of other CCR1-dependent chemokines. SB202190 inhibited HCC-4-induced chemotaxis in a dose-dependent manner (P < 0.01). HCC-4 induces p38 activation in both a time and dose-dependent manner. However, such p38 activation was not induced by other CCR1-dependent chemokines. To further investigate the differential effect of HCC-4, the Ca2+ mobilization was examined. HCC-4 induced no intracellular Ca2+ flux in contrast to other CCR1-dependent chemokines. These results indicate that HCC-4 transduces signals differently from other CCR1-dependent chemokines and may play different roles in the immune response.

IL-10 enhances CCL2 release and chemotaxis induced by CCL16 in human monocytes

CCL16 is a CC chemokine originally identified as a liver-expressed chemokine. Its expression has been detected in activated monocytes where it is up-regulated by stimulation with IL-10. This is in contrast with IL-10's inhibition of the expression of most chemokines. CCL16 is chemotactic for monocytes, lymphocyte and dendritic cells. We investigated whether CCL16 displays biological activities other than chemotaxis and whether IL-10 affects monocyte response to CCL16. We show that CCL16 induces the expression of CCL2 at the mRNA and protein level, but does not affect that of CCL5, CCL18 and proinflammatory cytokines. This effect was prevented by treatment with pertussis toxin and may thus be mediated by G-protein-coupled receptors. IL-10 markedly increased CCL2 production induced by CCL16, but suppressed that of CXCL8. It also enhanced the chemotactic response to CCL16. Addition of antibodies blocking CCR1, but not CCR8, prevented this enhanced chemotactic response and suggested that CCR1 is primarily involved. We propose that IL-10 modulates the effects of CCL16 on monocytes by increasing their CCR1-dependent response. The coordinated secretion of CCL16 and IL-10 may thus enhance monocyte infiltration.

Involvement of CC chemokine ligand 18 (CCL18) in normal and pathological processes

CC chemokine ligand 18 (CCL18) was originally discovered as pulmonary and activation-regulated chemokine (PARC), dendritic cell (DC)-chemokine 1 (DC-CK1), alternative macrophage activation-associated CC chemokine-1 (AMAC-1), and macrophage inflammatory protein-4 (MIP-4). CCL18 primarily targets lymphocytes and immature DC, although its agonistic receptor remains unknown so far. CCL18 is mainly expressed by a broad range of monocytes/macrophages and DC. A more profound understanding of the various activation programs and functional phenotypes of these producer cells might give a better insight in the proinflammatory versus anti-inflammatory role of this CC chemokine. It is interesting that CCL18 is constitutively present at high levels in human plasma and likely contributes to the physiological homing of lymphocytes and DC and to the generation of primary immune responses. Furthermore, enhanced CCL18 production has been demonstrated in several diseases, including various malignancies and inflammatory joint, lung, and skin diseases. The lack of a rodent counterpart for human CCL18 sets all hope on primate animal models to further elucidate the importance of CCL18 in vivo. This review will address these different aspects in more detail.

The expression of LEC/CCL16, a powerful inflammatory chemokine, is upregulated in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of unknown aetiology and pathogenesis. The presence in the colonic mucosa of reactive cells expressing proinflammatory cytokines and chemokines is associated with high levels of IL-10, an anti-inflammatory cytokine. Our aim was to investigate the role of IL-10 and the beta chemokine LEC/CCL16 selectively up-regulated by IL-10 in inflammatory cell recruitment and cytokine and chemokine production during UC. We studied histologically, immunohistochemically and ultrastructurally colonic biopsies from 20 active UC patients and 10 control specimens taken far from any macroscopically detectable lesion in age and sex-matched patients with noninflammatory bowel disease. In active UC, immature dendritic cells (DCs) in the LP are associated with IL-10 in the T cell rich area. Furthermore, most of the LP-infiltrating macrophages strongly expressed LEC/CCL16, a chemokine upregulated by IL-10. To evaluate if LEC/CCL16 plays a role in the inflammatory reaction present in UC, we performed morphological studies in mice injected s.c. with syngeneic tumor cells engineered to produce LEC/CCL16. We found that the LEC protein locally released by LEC-gene-transfected tumor cells is a potent proinflammatory chemokine that induces the recruitment of a reactive infiltrate, and an angiogenic process mirroring that in human UC.

Liver-expressed chemokine/CC chemokine ligand 16 attracts eosinophils by interacting with histamine H4 receptor

Liver-expressed chemokine (LEC)/CCL16 is a human CC chemokine that is constitutively expressed by the liver parenchymal cells and present in the normal plasma at high concentrations. Previous studies have shown that CCL16 is a low-affinity ligand for CCR1, CCR2, CCR5, and CCR8 and attracts monocytes and T cells. Recently, a novel histamine receptor termed type 4 (H4) has been identified and shown to be selectively expressed by eosinophils and mast cells. In this study, we demonstrated that CCL16 induced pertussis toxin-sensitive calcium mobilization and chemotaxis in murine L1.2 cells expressing H4 but not those expressing histamine receptor type 1 (H1) or type 2 (H2). CCL16 bound to H4 with a K(d) of 17 nM. By RT-PCR, human and mouse eosinophils express H4 but not H3. Accordingly, CCL16 induced efficient migratory responses in human and mouse eosinophils. Furthermore, the responses of human and mouse eosinophils to CCL16 were effectively suppressed by thioperamide, an antagonist for H3 and H4. Intravenous injection of CCL16 into mice induced a rapid mobilization of eosinophils from bone marrow to peripheral blood, which was also suppressed by thioperamide. Collectively, CCL16 is a novel functional ligand for H4 and may have a role in trafficking of eosinophils.

Anti-tumor activity of chemokine is affected by both kinds of tumors and the activation state of the host’s immune system: implications for chemokine-based cancer immunotherapy

In this study, we screened the anti-tumor activity of murine chemokines including CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1 by inoculating murine B16BL6, CT26, or OV-HM tumor cells, all of which were transfected with chemokine-expressing fiber-mutant adenovirus vector, into immunocompetent mice. A tumor-suppressive effect was observed in mice inoculated with CCL19/B16BL6 and XCL1/B16BL6, and CCL22/OV-HM showed considerable retardation in tumor growth. In the cured mice inoculated with CCL22/OV-HM, a long-term specific immune protection against parental tumor was developed. However, we were unable to identify the chemokine that had a suppressive activity common to all three tumor models. Furthermore, an experiment using chemokine-transfected B16BL6 cells was also performed on mice sensitized with melanoma-associated antigen. A drastic enhancement of the frequency of complete rejection was observed in mice inoculated with CCL17-, CCL19-, CCL22-, and CCL27-transfected B16BL6. Altogether, our results suggest that the tumor-suppressive activity of chemokine-gene immunotherapy is greatly influenced by the kind of tumor and the activation state of the host's immune system.

Cytosolic phospholipase A2 plays a key role in the pathogenesis of multiple sclerosis-like disease

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that results in motor and sensory deficits. Although MS and its animal model, experimental autoimmune encephalomyelitis (EAE), are thought to be T cell-mediated diseases, the mechanisms underlying the lesions in the CNS are not fully understood. We propose that a strong candidate as a central mediator in evoking the complex pathological changes seen in MS and EAE is the enzyme cytosolic phospholipase A2 (cPLA2). One of the metabolic products of this enzyme is pro-inflammatory, while the other induces myelin breakdown, demyelination, and chemokine/cytokine expression. We provide evidence that cPLA2 is highly expressed in EAE lesions and show that blocking this enzyme leads to a remarkable reduction in the onset and progression of EAE.

Intralesional Injection of Adenovirus Encoding CC Chemokine Ligand 16 Inhibits Mammary Tumor Growth and Prevents Metastatic-Induced Death after Surgical Removal of the Treated Primary Tumor

The CC chemokine ligand (CCL)16 exerts chemotactic activity on human monocytes and lymphocytes. Although no murine homologous has been defined, the TSA mouse adenocarcinoma cells engineered to express human CCL16 are rapidly rejected by syngenic mice. An adenovirus encoding CCL16 (AdCCL16) was generated using a Cre-Lox-based system and was used to determine whether this chemokine might also block pre-existing tumors. Both recombinant and viral CCL16 showed in vitro chemotactic activity for murine CD4(+) and CD8(+) lymphocytes and dendritic cells (DC). AdCCL16, but not the control empty vector, when injected in established nodules significantly delayed tumor growth. Immunohistochemistry revealed accumulation of CD4(+) and CD8(+) T cells and DC in the treated tumors as well as in draining lymph nodes. DC from such lymph nodes stimulated IFN-gamma by a T cell clone specific for the known TSA tumor-associated Ag (TAA), suggesting the tumor origin of these cells. Lymphocytes from the same nodes showed specific CTL activity against TSA tumor cells and their immunodominant TAA peptide. Antitumor activity required CD4, CD8, and IFN-gamma production, as shown using subset-depleted and knockout mice. Despite the robust and rapid immune response triggered by intratumoral injection of AdCCL16, the lesions were not completely rejected; however, the same treatment given before surgical excision of primary lesions prevented metastatic spread and cured 63% of mice bearing the 4T1 mammary adenocarcinoma, which is perhaps the most compelling model of spontaneous metastasis.

Selective induction of Th2-attracting chemokines CCL17 and CCL22 in human B cells by latent membrane protein 1 of Epstein-Barr virus

Chemokines are likely to play important roles in the pathophysiology of diseases associated with Epstein-Barr virus (EBV). Here, we have analyzed the repertoire of chemokines expressed by EBV-infected B cells. EBV infection of B cells induced expression of TARC/CCL17 and MDC/CCL22, which are known to attract Th2 cells and regulatory T cells via CCR4, and also upregulated constitutive expression of MIP-1 alpha/CCL3, MIP-1 beta/CCL4, and RANTES/CCL5, which are known to attract Th1 cells and cytotoxic T cells via CCR5. Accordingly, EBV-immortalized B cells secreted these chemokines, especially CCL3, CCL4, and CCL22, in large quantities. EBV infection or stable expression of LMP1 also induced CCL17 and CCL22 in a B-cell line, BJAB. The inhibitors of the TRAF/NF-kappa B pathway (BAY11-7082) and the p38/ATF2 pathway (SB202190) selectively suppressed the expression of CCL17 and CCL22 in EBV-immortalized B cells and BJAB-LMP1. Consistently, transient-transfection assays using CCL22 promoter-reporter constructs demonstrated that two NF-kappa B sites and a single AP-1 site were involved in the activation of the CCL22 promoter by LMP1. Finally, serum CCL22 levels were significantly elevated in infectious mononucleosis. Collectively, LMP1 induces CCL17 and CCL22 in EBV-infected B cells via activation of NF-kappa B and probably ATF2. Production of CCL17 and CCL22, which attract Th2 and regulatory T cells, may help EBV-infected B cells evade immune surveillance by Th1 cells. However, the concomitant production of CCL3, CCL4, and CCL5 by EBV-infected B cells may eventually attract Th1 cells and cytotoxic T cells, leading to elimination of EBV-infected B cells at latency III and to selection of those with limited expression of latent genes.

Mobilization of dendritic cell precursors into the circulation by administration of MIP-1alpha in mice

BACKGROUND

Dendritic cells (DCs) play a central role in immune responses and may be useful adjuvants for tumor vaccine therapy. We previously reported that F4/80(-)B220(-)CD11c(+) DC precursors expressing the CC chemokine receptors CCR1 and CCR5 are mobilized rapidly into the circulation in mice injected with Propionibacterium acnes and are recruited into inflammatory tissue by macrophage inflammatory protein 1alpha (MIP-1alpha), which binds to CCR1 and CCR5. Here we investigate the mechanisms of DC precursor mobilization and the antitumor effect of these cells in mice.

METHODS

Numbers of DC precursors in peripheral blood were determined in P. acnes-treated mice (groups of 10 C57BL/B6 [B6] wild-type mice, CCR1(-/-) mice, CCR5(-/-) mice, and B6 mice treated with antibody to MIP-1alpha or control antibody) and in B6 mice injected with recombinant MIP-1alpha. MIP-1alpha-mobilized DC precursors matured by treatment with granulocyte-macrophage colony-stimulating factor, interleukin 4, and tumor necrosis factor-alpha and pulsed with B16 melanoma lysates were assayed for their ability to confer protective immunity against tumor challenge in vivo and to induce cytotoxic T lymphocytes against B16 tumor cells in vitro.

RESULTS

The recruitment of DC precursors into the circulation by P. acnes administration was higher in B6 mice (12.6%, 95% confidence interval [CI] = 9.1% to 16.1%) than in CCR1(-/-) (9.0%, 95% CI = 7.5% to 10.5%), CCR5(-/-) (6.3%, 95% CI = 5.2% to 7.3%), or anti-MIP-1alpha antibody-treated (6.6%, 95% CI = 5.7% to 7.5%) mice. Injection of MIP-1alpha also mobilized DC precursors into the circulation (13.1%, 95% CI = 10.8% to 15.6%). Matured MIP-1alpha-mobilized-DC precursors pulsed with B16 tumor lysates elicited B16-specific antitumor immunity in vitro and in vivo.

CONCLUSIONS

MIP-1alpha and its receptors are important in recruiting DC precursors into the circulation. DC precursors mobilized rapidly by MIP-1alpha may provide sufficient useful DC precursors for DC-based vaccination in cancer treatment.

CCL16/LEC powerfully triggers effector and antigen-presenting functions of macrophages and enhances T cell cytotoxicity

The human CC chemokine CCL16, a liver-expressed chemokine, enhances the killing activity of mouse peritoneal macrophages by triggering their expression of tumor necrosis factor alpha (TNF-alpha) and Fas ligand. Macrophages also respond to CCL16 by enhancing their production of monocyte chemoattractant protein-1, regulated on activation, normal T cells expressed and secreted chemokines, and interleukin (IL)-1 beta, TNF-alpha, and IL-12. The effect of CCL16 is almost as strong as that of lipopolysaccharide and interferon-gamma, two of the best macrophage activators. Moreover, CCL16-activated macrophages overexpress membrane CD80, CD86, and CD40 costimulatory molecules and extensively phagocytose tumor cell debris. On exposure to such debris, they activate a strong, tumor-specific, cytolytic response in virgin T cells. Furthermore, cytolytic T cells generated in the presence of CCL16 display a higher cytotoxicity and activate caspase-8 in tumor target cells. This ability to activate caspase-8 depends on their overexpression of TNF-alpha and Fas ligand induced by CCL16. These data reveal a new function for CCL16 in the immune-response scenario. CCL16 significantly enhances the effector and the antigen-presenting function of macrophages and augments T cell lytic activity.

Cutting edge: SR-PSOX/CXC chemokine ligand 16 mediates bacterial phagocytosis by APCs through its chemokine domain

SR-PSOX and CXC chemokine ligand (CXCL)16, which were originally identified as a scavenger receptor and a transmembrane-type chemokine, respectively, are indicated to be identical. In this study, we demonstrate that membrane-bound SR-PSOX/CXCL16 mediates adhesion and phagocytosis of both Gram-negative and Gram-positive bacteria. Importantly, our prepared anti-SR-PSOX mAb, which suppressed chemotactic activity of SR-PSOX, significantly inhibited bacterial phagocytosis by human APCs including dendritic cells. Various scavenger receptor ligands inhibited the bacterial phagocytosis of SR-PSOX. In addition, the recognition specificity for bacteria was determined by only the chemokine domain of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 may play an important role in facilitating uptake of various pathogens and chemotaxis of T and NKT cells by APCs through its chemokine domain.

HGF-, EGF-, and dexamethasone-induced gene expression patterns during formation of tissue in hepatic organoid cultures

Corticosteroids, hepatocyte growth factor (HGF), and epidermal growth factor (EGF) play important roles in hepatic biology. We have previously shown that these molecules are required for formation of tissue with specific histology in complex organoid cultures. Dexamethasone suppresses growth and induces hepatocyte maturation; HGF and EGF are needed for formation of the nonepithelial elements. All three are needed for formation of the biliary epithelium. The gene expression patterns by which corticosteroids, HGF, and EGF mediate their effects in hepatic tissue formation are distinct. These patterns affect many gene families and are described in detail. In terms of main findings, dexamethasone induces expression of both HNF4 and C/EBPalpha, essential transcription factors for hepatocyte differentiation. It suppresses hepatocyte growth by suppressing many molecules associated with growth in liver and other tissues, including IL-6, CXC-chemokine receptor, amphiregulin, COX-2, HIF, etc. HGF and EGF induce all members of the TGF-beta family. They also induced multiple CNS-related genes, probably associated with stellate cells. Dexamethasone, as well as HGF and EGF, induces expression of HNF6-beta, associated with biliary epithelium formation. Combined addition of all three molecules is associated with mature histology in which hepatocyte and biliary lineages are separate and HNF4 is expressed only in hepatocyte nuclei. In conclusion, the results provide new and surprising information on the gene expression alterations by which corticosteroids, HGF, and EGF exert their effects on formation of hepatic tissue. The results underscore the usefulness of the organoid cultures for generating information on histogenesis, which cannot be obtained by other culture or whole animal models.

Comparative DNA sequence analysis of mouse and human CC chemokine gene clusters

The CC chemokines are a closely related subfamily of the chemokine superfamily. Most of the CC chemokine genes form a cluster on chromosome 11 in mice and chromosome 17 in humans. To date, 11 and 16 functional genes have been localized within the mouse and human clusters, respectively. Notably, some of the genes within these clusters appear to have no counterparts between the two species, and the orthologous relationships of some of the genes are difficult to establish solely on the basis of amino acid similarity. In this study, we have taken a comparative genomic approach to reveal some of the features that may be involved in the dynamic evolution of these gene clusters. We sequenced a 122-kb region containing five chemokine genes of the mouse CC cluster. This mouse sequence was combined with those determined by the Mouse Genome Sequencing Project, and the entire sequence of the mouse CC cluster was compared with that of the corresponding cluster in the human genome by percent identity plot and dot-plot analyses. Although no additional chemokine genes have been found in these clusters, our analysis has revealed that numerous gene rearrangements have occurred even after the diversification of rodents and primates, resulting in several species-specific chemokine genes and pseudogenes. In addition, phylogenetic analysis and comparison of the genomic sequences unambiguously identified the orthologous relationships of some of the chemokine genes in the mouse and human CC gene clusters.

Presence of high contents of thymus and activation-regulated chemokine in platelets and elevated plasma levels of thymus and activation-regulated chemokine and macrophage-derived chemokine in patients with atopic dermatitis

BACKGROUND

T(H)2 cells and eosinophils selectively express CC chemokine receptor 4 and CCR3, respectively, and their chemokine ligands are likely to play important roles in the pathogenesis of atopic dermatitis (AD).

OBJECTIVE

The purpose of this study was to demonstrate the presence of thymus and activation-regulated chemokine (TARC) in platelets and its release during clotting and to evaluate the circulating levels of TARC, macrophage-derived chemokine (MDC), and eotaxin in control subjects and patients with AD.

METHODS

We compared plasma and serum contents of TARC, MDC, and eotaxin. We measured TARC contents in platelet lysates. We analyzed the correlation of plasma levels of TARC, MDC, and eotaxin with various clinicolaboratory parameters in patients with AD.

RESULTS

Serum contents of TARC rapidly increased during clotting, whereas those of MDC and eotaxin increased only slightly. We demonstrated that platelets contained TARC, and its levels were dramatically elevated in patients with AD. Platelets also released TARC on stimulation with thrombin. We therefore evaluated circulating levels of these chemokines in control subjects and patients with AD by using plasma samples. Plasma TARC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with severity scoring of atopic dermatitis (SCORAD) index (r = 0.665, P <.00001), serum lactate dehydrogenese levels (r = 0.696, P =.00001), eosinophil counts (r = 0.381, P =.007), and platelet counts (r = 0.562, P <.0001). Similarly, plasma MDC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with SCORAD index (r = 0.727, P <.0001), serum lactate dehydrogenese levels (r = 0.861, P <.0001), eosinophil counts (r = 0.505, P =.005), and platelet counts (r = 0.370, P =.01). On treatment, plasma TARC and MDC levels were dramatically decreased in accordance with improved SCORAD scores (P =.0012 and P =.0007, respectively). On the other hand, plasma eotaxin levels did not show any significant increase or correlation with any of the clinical parameters in patients with AD.

CONCLUSION

Platelets from patients with AD contain high levels of TARC. Thus platelets might play an important role in AD pathogenesis by releasing T(H)2-attracting TARC on activation. Furthermore, circulating levels of TARC and MDC, but not those of eotaxin, correlate well with the disease activity of AD.