Cinacalcet for managing secondary hyperparathyroidism in dialysis patients in clinical practice in Belgium: a 16-month observational study (ECHO-B)

In Belgium, the calcimimetic cinacalcet is initially reimbursed for < or = 4 months in dialysis patients with secondary hyperparathyroidism (SHPT) and intact parathyroid hormone (iPTH) > or = 800 pg/mL, or iPTH 300-800 pg/ mL and Ca x P > 55 mg 2/dL2 despite > or = 6 months' optimal treatment with vitamin D sterols and/or phosphate binders. The Belgian, multicentre, observational study ECHO-B evaluated cinacalcet in such patients. Patients who began cinacalcet treatment after March 1, 2007 were eligible. Data were collected retro/prospectively from 6 months before until 16 months after starting cinacalcet (whether or not cinacalcet was continued). Median iPTH was markedly elevated (816 [IQR 551-991] pg/mL) at baseline (the time of starting cinacalcet), but decreased continuously over the course of the study, reaching a value of 414 pg/mL (IQR 240-641; median change -41%) at 4 months, 335 pg/mL (IQR 159-616; -60%) at 12 months and 250 pg/mL (IQR 172-436; -64%) at 16 months. Reductions in serum calcium (-7%) and phosphorus (-13%) were already (near) maximal at 4 months. The primary outcome (iPTH 150-300 pg/mL and/or a > or = 30% reduction within 4 months of starting cinacalcet; criterion for continued reimbursement in Belgium) was achieved in 65/81 patients (80%; 95% CI 72-89%). Results show that in dialysis patients with SHPT in real-life clinical practice, mineral metabolism improves after starting cinacalcet: our study findings suggest that PTH levels may continue decreasing after 12 months' treatment in this setting.

Expression of angiostatic platelet factor-4var/CXCL4L1 counterbalances angiogenic impulses of vascular endothelial growth factor, interleukin-8/CXCL8, and stromal cell-derived factor 1/CXCL12 in esophageal and colorectal cancer

Chemokines influence tumor progression through regulation of leukocyte chemotaxis, angiogenesis, and metastasis. In this study, the regulated expression of angiogenic (stromal cell-derived factor [SDF]-1/CXCL12 and interleukin [IL]-8/CXCL8) and angiostatic (platelet factor [PF]-4var/CXCL4L1 and inducible protein [IP-10]/CXCL10) chemokines was examined in human colorectal and esophageal cancer. In HCT 116 and HCT-8 colorectal adenocarcinoma cells, the production of IL-8 immunoreactivity was up-regulated by IL-1beta, tumor necrosis factor (TNF)-alpha, the toll-like receptor (TLR) ligands double-stranded RNA and peptidoglycan and phorbol ester. Increased PF-4 and synergistic IL-8 and IP-10 induction in carcinoma cells after stimulation with IL-1beta plus TNF-alpha or interferon-gamma was demonstrated by enzyme-linked immunosorbent assay, quantitative reverse transcriptase polymerase chain reaction, or immunocytochemistry. In addition, IL-8 from HT-29 colorectal adenocarcinoma cells was molecularly identified as intact chemokine, as well as NH(2)-terminally truncated, more active IL-8(6-77). The presence of PF-4var, SDF-1, and vascular endothelial growth factor (VEGF) was evidenced by immunohistochemistry in surgical samples from 51 patients operated on for colon adenocarcinoma (AC), esophageal AC, or esophageal squamous cell carcinoma (SCC). PF-4var was strongly detected in colorectal cancer, whereas its expression in esophageal cancer was rather weak. Staining for SDF-1 was almost negative in esophageal SCC, whereas a more intense and frequent staining was observed in AC of the esophagus and colon. Staining for VEGF was moderately to strongly positive in all 3 types of cancer, although less prominent in esophageal AC. The heterogenous expression of angiogenic (IL-8, SDF-1) as well as angiostatic (IP-10, PF-4var) chemokines not only within the tumor and between the different cases but also between the different tumor cell types may indicate a distinct role of the various chemokines in the complex process of tumor development.

Citrullination of CXCL8 by peptidylarginine deiminase alters receptor usage, prevents proteolysis, and dampens tissue inflammation

Biological functions of proteins are influenced by posttranslational modifications such as on/off switching by phosphorylation and modulation by glycosylation. Proteolytic processing regulates cytokine and chemokine activities. In this study, we report that natural posttranslational citrullination or deimination alters the biological activities of the neutrophil chemoattractant and angiogenic cytokine CXCL8/interleukin-8 (IL-8). Citrullination of arginine in position 5 was discovered on 14% of natural leukocyte-derived CXCL8(1–77), generating CXCL8(1–77)Cit₅. Peptidylarginine deiminase (PAD) is known to citrullinate structural proteins, and it may initiate autoimmune diseases. PAD efficiently and site-specifically citrullinated CXCL5, CXCL8, CCL17, CCL26, but not IL-1β. In comparison with CXCL8(1–77), CXCL8(1–77)Cit₅ had reduced affinity for glycosaminoglycans and induced less CXCR2-dependent calcium signaling and extracellular signal-regulated kinase 1/2 phosphorylation. In contrast to CXCL8(1–77), CXCL8(1–77)Cit₅ was resistant to thrombin- or plasmin-dependent potentiation into CXCL8(6–77). Upon intraperitoneal injection, CXCL8(6–77) was a more potent inducer of neutrophil extravasation compared with CXCL8(1–77). Despite its retained chemotactic activity in vitro, CXCL8(1–77)Cit₅ was unable to attract neutrophils to the peritoneum. Finally, in the rabbit cornea angiogenesis assay, the equally potent CXCL8(1–77) and CXCL8(1–77)Cit₅ were less efficient angiogenic molecules than CXCL8(6–77). This study shows that PAD citrullinates the chemokine CXCL8, and thus may dampen neutrophil extravasation during acute or chronic inflammation.

Synergy between coproduced CC and CXC chemokines in monocyte chemotaxis through receptor-mediated events

CC and CXC chemokines coinduced in fibroblasts and leukocytes by cytokines and microbial agents determine the number of phagocytes infiltrating into inflamed tissues. Interleukin-8/CXCL8 and stromal cell-derived factor-1/CXCL12 significantly and dose-dependently increased the migration of monocytes, expressing the corresponding CXC chemokine receptors CXCR2 and CXCR4, toward suboptimal concentrations of the monocyte chemotactic proteins CCL2 or CCL7. These findings were confirmed using different chemotaxis assays and monocytic THP-1 cells. In contrast, the combination of two CC chemokines (CCL2 plus CCL7) or two CXC chemokines (CXCL8 plus CXCL12) did not provide synergy in monocyte chemotaxis. These data show that chemokines competing for related receptors and using similar signaling pathways do not synergize. Receptor heterodimerization is probably not essential for chemokine synergy as shown in CXCR4/CCR2 cotransfectants. It is noteworthy that CCL2 mediated extracellular signal-regulated kinase 1/2 phosphorylation and calcium mobilization was significantly enhanced by CXCL8 in monocytes, indicating cooperative downstream signaling pathways during enhanced chemotaxis. Moreover, in contrast to intact CXCL12, truncated CXCL12(3-68), which has impaired receptor signaling capacity but can still desensitize CXCR4, was unable to synergize with CCL2 in monocytic cell migration. Furthermore, AMD3100 and RS102895, specific CXCR4 and CCR2 inhibitors, respectively, reduced the synergistic effect between CCL2 and CXCL12 significantly. These data indicate that for synergistic interaction between chemokines binding and signaling of the two chemokines via their proper receptors is necessary.

Stimulation of angiostatic platelet factor-4 variant (CXCL4L1/PF-4var) versus inhibition of angiogenic granulocyte chemotactic protein-2 (CXCL6/GCP-2) in normal and tumoral mesenchymal cells

Chemokines affect inflammation and cancer through leukocyte attraction and angiogenesis. Here, we demonstrate that CXCL4L1/platelet factor-4 variant (PF-4var), a highly angiostatic chemokine, is poorly chemotactic for phagocytes and is inducible in monocytes by inflammatory mediators but remained undetectable in macrophages and neutrophils. In addition, CXCL4L1/PF-4var production by mesenchymal tumor cells was evidenced in vitro and in vivo by specific ELISA and immunohistochemistry. CXCL4L1/PF-4var, but not CXCL4/PF-4, was coinduced with the angiogenic chemokine CXCL6/granulocyte chemotactic protein-2 (GCP-2) by cytokines, e.g., IL-1beta and IL-17, in sarcoma cells, but not in diploid fibroblasts. Furthermore, the induction of CXCL6/GCP-2 in endothelial cells by IL-1beta was enhanced synergistically by TNF-alpha but inhibited by IFN-gamma, which synergized with IL-1beta to produce the angiostatic CXCL10/IFN-gamma-induced protein-10. These findings indicate that the equilibrium between angiostatic and angiogenic factors during inflammation and tumor progression is rather complex and differs depending on the chemokine, cell type, and stimulus. Selective intervention in the chemokine network may drastically disturb this delicate balance of angiogenesis and tissue repair. Application of angiostatic CXCL4L1/PF-4var without attraction of protumoral phagocytes may be beneficial in cancer therapy.

Hypoxia enhances CXCR4 expression in human microvascular endothelial cells and human melanoma cells

The influence of environmental factors (cytokines, matrix components, serum factors and O(2) level) on expression of receptors for angiogenic versus angiostatic CXC chemokines in human microvascular endothelial cells has not been extensively investigated. Our semi-quantitative RT-PCR analysis demonstrated that TNF-alpha and IFN-gamma repressed CXCR4 mRNA levels in immortalized human microvascular endothelial HMEC-1 cells after 4 h, whereas only TNF-alpha displayed inhibitory activity in primary human microvascular endothelial cells (HMVEC). CXCR4 mRNA expression was not affected by VEGF, GM-CSF, IL-1beta or various basal membrane matrix components, but was significantly up-regulated after serum starvation and/or hypoxic treatment of the microvascular endothelial cells. The alternative CXCL12 receptor, CXCR7/RDC1, was also up-regulated by hypoxia in HMEC-1 cells, although less consistently than CXCR4. Furthermore, hypoxia and serum starvation were required for cell surface display of CXCR4 and CXCL12 induction of ERK activation in HMEC-1 cells. In contrast, CXCR2 and CXCR3 mRNA levels remained, respectively, low and undetectable under all the conditions tested, and surface expression of CXCR2, CXCR3 and CXCR7 on the HMEC- 1 cells could not be demonstrated by FACS. In the human SK-MEL-5 melanoma cell line, CXCR4 mRNA expression was also increased under hypoxic conditions, whereas CXCR2 mRNA levels remained low and levels of CXCR3 and CXCR7 were undetectable. However, immunohistochemical staining of human metastatic melanoma sections demonstrated that CXCR2, CXCR3, CXCR4 and CXCR7 are expressed on tumor cells and, to a lesser extent, on endothelial cells. These results demonstrate that the tumor microenvironment regulates chemokine receptor expression through both cytokine and oxygen levels.

Proteolytic processing of CXCL11 by CD13/aminopeptidase N impairs CXCR3 and CXCR7 binding and signaling and reduces lymphocyte and endothelial cell migration

CXCR3 ligands were secreted by tissue fibroblasts and peripheral blood-derived mononuclear leukocytes in response to interferon-gamma (IFN-gamma) and Toll-like receptor (TLR) ligands. Subsequent purification and identification revealed the presence of truncated CXCL11 variants missing up to 6 amino acids. In combination with CD26/dipeptidyl peptidase IV, the metalloprotease aminopeptidase N (APN), identical to the myeloid cell marker CD13, rapidly processed CXCL11, but not CXCL8, to generate truncated CXCL11 forms. Truncated CXCL11 had reduced binding, signaling, and chemotactic properties for lymphocytes and CXCR3- or CXCR7-transfected cells. CD13/APN-truncated CXCL11 failed to induce an intracellular calcium increase but was still able to bind and desensitize CXCR3 for intact CXCL11 signaling. CXCL11 efficiently bound to CXCR7, but CXCL11 was not able to induce calcium signaling or ERK1/2 or Akt phosphorylation through CXCR7. CD26-truncated CXCL11 failed to attract lymphocytes but still inhibited microvascular endothelial cell (HMVEC) migration. However, further processing of CXCL11 by CD13 resulted in significant reduction of inhibition of HMVEC migration. Taken together, during inflammation or cancer, CXCL11 processing by CD13 may lead to a reduced number of tumor-infiltrating lymphocytes and in a more angiogenic environment.

Coexpression and interaction of CXCL10 and CD26 in mesenchymal cells by synergising inflammatory cytokines: CXCL8 and CXCL10 are discriminative markers for autoimmune arthropathies

Leukocyte infiltration during acute and chronic inflammation is regulated by exogenous and endogenous factors, including cytokines, chemokines and proteases. Stimulation of fibroblasts and human microvascular endothelial cells with the inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor alpha (TNF-alpha) combined with either interferon-alpha (IFN-alpha), IFN-beta or IFN-gamma resulted in a synergistic induction of the CXC chemokine CXCL10, but not of the neutrophil chemoattractant CXCL8. In contrast, simultaneous stimulation with different IFN types did not result in a synergistic CXCL10 protein induction. Purification of natural CXCL10 from the conditioned medium of fibroblasts led to the isolation of CD26/dipeptidyl peptidase IV-processed CXCL10 missing two NH2-terminal residues. In contrast to intact CXCL10, NH2-terminally truncated CXCL10(3-77) did not induce extracellular signal-regulated kinase 1/2 or Akt/protein kinase B phosphorylation in CXC chemokine receptor 3-transfected cells. Together with the expression of CXCL10, the expression of membrane-bound CD26/dipeptidyl peptidase IV was also upregulated in fibroblasts by IFN-gamma, by IFN-gamma plus IL-1beta or by IFN-gamma plus TNF-alpha. This provides a negative feedback for CXCL10-dependent chemotaxis of activated T cells and natural killer cells. Since TNF-alpha and IL-1beta are implicated in arthritis, synovial concentrations of CXCL8 and CXCL10 were compared in patients suffering from crystal arthritis, ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis. All three groups of autoimmune arthritis patients (ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis) had significantly increased synovial CXCL10 levels compared with crystal arthritis patients. In contrast, compared with crystal arthritis, only rheumatoid arthritis patients, and not ankylosing spondylitis or psoriatic arthritis patients, had significantly higher synovial CXCL8 concentrations. Synovial concentrations of the neutrophil chemoattractant CXCL8 may therefore be useful to discriminate between autoimmune arthritis types.

TLR ligands and cytokines induce CXCR3 ligands in endothelial cells: enhanced CXCL9 in autoimmune arthritis

CXC chemokines are potent attractants of neutrophil granulocytes, T cells or natural killer cells. Toll-like receptors (TLR) recognize microbial components and are also activated by endogenous molecules possibly implicated in autoimmune arthritis. In contrast to CXC chemokine ligand 8 (CXCL8), no CXC chemokine receptor 3 (CXCR3) ligand (ie CXCL9, CXCL10 and CXCL11) was induced by bacterial TLR ligands in human microvascular endothelial cells (HMVEC). However, peptidoglycan (PGN), double-stranded (ds) RNA or lipopolysaccharide (LPS) (TLR2, TLR3 or TLR4 ligands, respectively) synergized with interferon-gamma (IFN-gamma) at inducing CXCL9 and CXCL10. In contrast, enhanced CXCL11 secretion was only obtained when IFN-gamma was combined with TLR3 ligand. Furthermore, flagellin, loxoribine and unmethylated CpG oligonucleotide (TLR5, TLR7 and TLR9 ligands, respectively) did not enhance IFN-gamma-dependent CXCR3 ligand production in HMVEC. In analogy with TLR ligands, tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1beta), in combination with IFN-gamma, synergistically induced CXCL9 and CXCL11 in HMVEC and human fibroblasts, two fundamental cell types delineating the joint cavity. Etanercept, a humanized soluble recombinant p75 TNF-receptor/IgG(1)Fc fusionprotein, neutralized synergistic CXCL9 production induced by TNF-alpha plus IFN-gamma, but not synergy between IFN-gamma and the TLR ligands PGN or LPS. Synovial chemokine concentrations exemplify the physiopathological relevance of the observed in vitro chemokine production patterns. In synovial fluids of patients with spondylarthropathies (ie ankylosing spondylitis or psoriatic arthritis) or rheumatoid arthritis, significantly enhanced CXCL9, but not CXCL11 levels, were detected compared to concentrations in synovial fluids of patients with metabolic crystal-induced arthritis. Thus, CXCL9 is an important chemokine in autoimmune arthritis.

Deletion of the COOH-terminal domain of CXC chemokine receptor 4 leads to the down-regulation of cell-to-cell contact, enhanced motility and proliferation in breast carcinoma cells

The CXC chemokine receptor 4 (CXCR4) contributes to the metastasis of human breast cancer cells. The CXCR4 COOH-terminal domain (CTD) seems to play a major role in regulating receptor desensitization and down-regulation. We expressed either wild-type CXCR4 (CXCR4-WT) or CTD-truncated CXCR4 (CXCR4-DeltaCTD) in MCF-7 human mammary carcinoma cells to determine whether the CTD is involved in CXCR4-modulated proliferation of mammary carcinoma cells. CXCR4-WT-transduced MCF-7 cells (MCF-7/CXCR4-WT cells) do not differ from vector-transduced MCF-7 control cells in morphology or growth rate. However, CXCR4-DeltaCTD-transduced MCF-7 cells (MCF-7/CXCR4-DeltaCTD cells) exhibit a higher growth rate and altered morphology, potentially indicating an epithelial-to-mesenchymal transition. Furthermore, extracellular signal-regulated kinase (ERK) activation and cell motility are increased in these cells. Ligand induces receptor association with beta-arrestin for both CXCR4-WT and CXCR4-DeltaCTD in these MCF-7 cells. Overexpressed CXCR4-WT localizes predominantly to the cell surface in unstimulated cells, whereas a significant portion of overexpressed CXCR4-DeltaCTD resides intracellularly in recycling endosomes. Analysis with human oligomicroarray, Western blot, and immunohistochemistry showed that E-cadherin and Zonula occludens are down-regulated in MCF-7/CXCR4-DeltaCTD cells. The array analysis also indicates that mesenchymal marker proteins and certain growth factor receptors are up-regulated in MCF-7/CXCR4-DeltaCTD cells. These observations suggest that (a) the overexpression of CXCR4-DeltaCTD leads to a gain-of-function of CXCR4-mediated signaling and (b) the CTD of CXCR4-WT may perform a feedback repressor function in this signaling pathway. These data will contribute to our understanding of how CXCR4-DeltaCTD may promote progression of breast tumors to metastatic lesions.

Chemokine receptor internalization and intracellular trafficking

The internalization and intracellular trafficking of chemokine receptors have important implications for the cellular responses elicited by chemokine receptors. The major pathway by which chemokine receptors internalize is the clathrin-mediated pathway, but some receptors may utilize lipid rafts/caveolae-dependent internalization routes. This review discusses the current knowledge and controversies regarding these two different routes of endocytosis. The functional consequences of internalization and the regulation of chemokine receptor recycling will also be addressed. Modifications of chemokine receptors, such as palmitoylation, ubiquitination, glycosylation, and sulfation, may also impact trafficking, chemotaxis and signaling. Finally, this review will cover the internalization and trafficking of viral and decoy chemokine receptors.

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.

Synergistic induction of CXCL9 and CXCL11 by Toll-like receptor ligands and interferon-gamma in fibroblasts correlates with elevated levels of CXCR3 ligands in septic arthritis synovial fluids

The synovial cavity constitutes the ideal stage to study the interplay between microbial Toll-like receptor (TLR) ligands and cytokines. Infiltrated leukocytes and synovial fibroblasts produce cytokine- and chemokine-induced proteases for remodeling the extracellular matrix. The regulation of chemokine function for attraction and activation of leukocytes constitutes a key feature in host immunity and resolution of inflammation after infection. Enhanced levels of the CXC chemokine ligand (CXCL9)/monokine induced by interferon-gamma (IFN-gamma) and CXCL11/IFN-inducible T cell alpha chemoattractant, two chemoattractants for activated T cells and natural killer cells, and ligands for CXC chemokine receptor 3 (CXCR3) were detected in the synovial fluid of septic arthritis compared with osteo- and crystal arthritis patients. In vitro, IFN-gamma and TLR3 ligation by double-stranded RNA (dsRNA) induced the expression of CXCL9 and CXCL11 in leukocytes and skin-muscle fibroblasts, whereas ligation of TLR2, TLR4, TLR5, and TLR9 by peptidoglycan (PGN), lipopolysaccharide (LPS), flagellin, and unmethylated CpG oligonucleotides, respectively, did not. PGN and LPS, but not unmethylated CpG oligonucleotides, even inhibited IFN-gamma-induced CXCL9 and CXCL11 expression in leukocytes. In sharp contrast, in fibroblasts, the TLR ligands PGN, dsRNA, LPS, and flagellin synergized with IFN-gamma for the production of CXCL9 and CXCL11. Although TLR ligands stimulate leukocytes to produce CXCL8/interleukin-8 during the early innate defense, they contribute less to the production of CXCR3 ligands, whereas fibroblasts are important sources of CXCR3 ligands. These results illustrate the complex interaction between cytokines and TLR ligands in infection.

PARC/CCL18 is a plasma CC chemokine with increased levels in childhood acute lymphoblastic leukemia

Chemokines play an important role in leukocyte mobilization, hematopoiesis, and angiogenesis. Tissue-specific expression of particular chemokines also influences tumor growth and metastasis. Here, the CC chemokine pulmonary and activation-regulated chemokine (PARC)/CCL18 was measured in pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML). Surprisingly, PARC immunoreactivity was consistently detected in plasma from healthy donors. After purification to homogeneity, the presence of intact PARC (1-69) and processed PARC (1-68) in normal human plasma was confirmed by sequence and mass spectrometry analysis. Furthermore, PARC serum levels were significantly increased in children with T-ALL and prepreB-ALL compared to control serum samples, whereas serum levels in AML and preB-ALL patients were not significantly different from controls. In contrast, the hemofiltrate CC chemokine-1 (HCC-1)/CCL14 was not found to be a biomarker in any of these patients' strata, whereas the cytokine interleukin-6 (IL-6) was significantly decreased in AML and prepreB-ALL. Stimulated leukocytic cell lines or lymphoblasts from patients produced IL-8/CXCL8 or macrophage inflammatory protein-1alpha (MIP-1alpha/CCL3) but not PARC, not even after IL-4 or IL-10 treatment. However, PARC was produced by superantigen or IL-4 stimulated monocytes co-cultured with lymphocytes or lymphoblastic cells. Serum PARC levels thus constitute a novel leukemia marker, possibly reflecting tumor/host cell interactions in the circulation.

The CC chemokine CCL20 and its receptor CCR6

CCL20, alternatively named liver and activation-regulated chemokine (LARC), macrophage inflammatory protein-3alpha (MIP-3alpha) or Exodus-1, is the only chemokine known to interact with CC chemokine receptor 6 (CCR6), a property shared with the antimicrobial beta-defensins. The ligand-receptor pair CCL20-CCR6 is responsible for the chemoattraction of immature dendritic cells (DC), effector/memory T-cells and B-cells and plays a role at skin and mucosal surfaces under homeostatic and inflammatory conditions, as well as in pathology, including cancer and rheumatoid arthritis. In this review, the discovery, the gene and protein structure, the in vitro biological activities, the cell and inducer specific expression and the tissue distribution of CCL20 and CCR6 are discussed.

The CXC chemokine GCP-2/CXCL6 is predominantly induced in mesenchymal cells by interleukin-1beta and is down-regulated by interferon-gamma: comparison with interleukin-8/CXCL8

Human granulocyte chemotactic protein-2 (GCP-2)/CXCL6 is a CXC chemokine that functionally uses both of the IL-8/CXCL8 receptors to chemoattract neutrophils but that is structurally most related to epithelial cell-derived neutrophil attractant-78 (ENA-78)/CXCL5. This study provides the first evidence that GCP-2 protein is, compared with IL-8, weakly produced by some sarcoma, but less by carcinoma cells, and is tightly regulated in normal mesenchymal cells. IL-1beta was the predominant GCP-2 inducer in fibroblasts, chondrocytes, and endothelial cells, whereas IL-8 was equally well up-regulated in these cells by TNF-alpha, measles virus, or double-stranded RNA (dsRNA). In contrast, lipopolysaccharide (LPS) was a relatively better stimulus for GCP-2 versus IL-8 in fibroblasts. IFN-gamma down-regulated the GCP-2 production in fibroblasts induced by IL-1beta, TNF-alpha, LPS, or dsRNA. The kinetics of GCP-2 induction by IL-1beta, LPS, or dsRNA in fibroblasts differed from those of IL-8. Freshly isolated peripheral blood mononuclear leukocytes, which are a good source of IL-8 and ENA-78, failed to produce GCP-2. However, lung macrophages and blood monocyte-derived macrophages produced GCP-2 in response to LPS. Quantitatively, secretion of GCP-2 always remained inferior to that of IL-8, despite the fact that the ELISA recognized all posttranslationally modified GCP-2 isoforms. The expression of GCP-2 was confirmed in vivo by immunohistochemistry. The patterns of producer cell types, inducers and kinetics and the quantities of GCP-2 produced, suggest a unique role for GCP-2 in physiologic and pathologic processes.

Identification of biologically active chemokine isoforms from ascitic fluid and elevated levels of CCL18/pulmonary and activation-regulated chemokine in ovarian carcinoma

Chemokines are important in leukocyte homeostasis, inflammation, angiogenesis, and metastasis. Here, the molecular diversity of chemokines present in ovarian carcinoma was studied by purifying the proteins to homogeneity from ascitic fluid. Biologically active intact CCL2 and processed CXCL8, CCL3, and CCL18 isoforms were recovered. CCL7 and CCL20 were also purified, but their levels were 10-fold lower compared with CXCL8, CCL2, and CCL3 and even 100-fold lower than the amounts of CCL18 isolated. In ascitic fluids from patients with ovarian carcinoma (n = 12), significantly higher levels of CXCL8 and CCL18 (2.0 versus 0.7 ng/ml (p = 0.01) and 120 versus 44 ng/ml (p = 0.0002), respectively) were detected compared with those in nonovarian carcinoma patients (n = 12). In contrast to CXCL8, CCL18 was not inducible in carcinoma cell lines. Immunostaining showed CCL18 expression in tumor-infiltrating cells with monocyte/macrophage morphology but not in the ovarian carcinoma cells. Our data demonstrate that biochemically heterogenous but biologically active forms of several chemokines are present at different concentrations in ovarian carcinoma ascitic fluid. This points to a delicate balance of chemokines in epithelial ovarian cancer and to a potentially major role for CXCL8 and CCL18 in this tumor.

Amino-terminal truncation of CXCR3 agonists impairs receptor signaling and lymphocyte chemotaxis, while preserving antiangiogenic properties

The interferon (IFN)-inducible chemokines, specifically, IFN-gamma-inducible protein-10 (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha-chemoattractant (I-TAC), share a unique CXC chemokine receptor (CXCR3). Recently, the highly specific membrane-bound protease and lymphocyte surface marker CD26/dipeptidyl peptidase IV (DPP IV) was found to be responsible for posttranslational processing of chemokines. Removal of NH(2)-terminal dipeptides by CD26/DPP IV alters chemokine receptor binding and signaling, and hence inflammatory and anti-human immunodeficiency virus (HIV) activities. CD26/DPP IV and CXCR3 are both markers for Th1 lymphocytes and, moreover, CD26/DPP IV is present in a soluble, active form in human plasma. This study reports that at physiologic enzyme concentrations CD26/DPP IV cleaved 50% of I-TAC within 2 minutes, whereas for IP-10 and Mig the kinetics were 3- and 10-fold slower, respectively. Processing of IP-10 and I-TAC by CD26/DPP IV resulted in reduced CXCR3-binding properties, loss of calcium-signaling capacity through CXCR3, and more than 10-fold reduced chemotactic potency. Moreover, IP-10 and I-TAC cleaved by CD26/DPP IV acted as chemotaxis antagonists and CD26/DPP IV-truncated IP-10 and Mig retained their ability to inhibit the angiogenic activity of interleukin-8 in the rabbit cornea micropocket model. These data demonstrate a negative feedback regulation by CD26/DPP IV in CXCR3-mediated chemotaxis without affecting the angiostatic potential of the CXCR3 ligands IP-10 and Mig.

Selective induction of CCL18/PARC by staphylococcal enterotoxins in mononuclear cells and enhanced levels in septic and rheumatoid arthritis

Chemokines are mediators of innate and acquired immunity. CCL18, also designated pulmonary and activation-regulated chemokine (PARC), dendritic cell-derived CC chemokine-1 (DC-CK1), alternative macrophage activation-associated CC chemokine-1 (AMAC-1) and macrophage inflammatory protein-4 (MIP-4), was for the first time isolated from peripheral blood mononuclear cells (PBMC) and biochemically characterized. We found that CCL18/PARC protein is spontaneously secreted by PBMC and is selectively induced in PBMC by staphylococcal enterotoxins (SEA, SEB) and IL-4, but not by IFN-gamma and the CXCL8/IL-8 inducers lipopolysaccharide (LPS) or Concanavalin A. Human fibroblasts, chondrocytes and endothelial cells did not produce CCL18/PARC in response to inflammatory mediators such as measles virus, double-stranded RNA, LPS or IL-1beta, whereas up to 150 ng/ml of CCL2/MCP-1 was induced under these conditions. In synovial fluids from septic and rheumatoid arthritis patients, fourfold-enhanced CCL18/PARC levels (150 ng/ml) were detected compared to those in crystal-induced arthritis and osteoarthritis. In septic arthritis, the synovial levels of CCL18/PARC were fivefold higher than those of CXCL8/IL-8. Immunochemistry revealed CD68(+) monocytes/macrophages as the main CCL18/PARC-producing cell type in both PBMC and arthritic synovial tissue. In addition, CD1a(+) blood dendritic cells expressed CCL18/PARC. These findings suggest that monocytic cells respond to Gram-positive bacterial infection by the production of CCL18/PARC in the synovial cavity.

Gene cloning of a new plasma CC chemokine, activating and attracting myeloid cells in synergy with other chemoattractants

Chemokines are important mediators of cell migration during inflammation and normal leukocyte trafficking. Inflammatory chemokines are induced in multiple cell types at sites of infection. Here, we describe a novel bovine CC chemokine, designated regakine-1, that is constitutively present at high concentrations in plasma. Cloning of its gene revealed an expected two intron/three exon organization, with a rather long first intron. In addition to a 21-residue signal peptide, the coding sequence corresponded to a 71-residue secreted protein. However, the natural regakine-1 protein missed the COOH-terminal lysine residue. Regakine-1 has only weak sequence similarity (<50% identical residues) with other animal or human chemokines. Northern blot analysis demonstrated regakine-1 RNA expression in spleen and lung. At physiological concentrations (30-100 ng/mL), natural 7.5 kDa regakine-1 stimulated gelatinase B release from neutrophils and chemoattracted immature myeloid HL-60 cells, as well as mature granulocytes. Regakine-1 was more potent on human myeloid cells than the human plasma CC chemokine hemofiltrate CC chemokine-1 (HCC-1). Moreover, regakine-1 synergized with the bacterial peptide N-formylmethionylleucylphenylalanine (fMLP), yielding a 10-fold increase in neutrophil chemotactic response above their additive effect. Regakine-1 did not compete with interleukin-8 (IL-8) for binding to neutrophils, nor did it affect fMLP-induced calcium signaling, suggesting that regakine-1 recognizes a different receptor. In view of its high constitutive plasma concentration, regakine-1 is believed to recruit myeloid cells into the circulation, whereas its synergy with other neutrophil chemoattractants suggests that it also enhances the inflammatory response to infection.

Biochemical and biological characterization of neutrophil chemotactic protein, a novel rabbit CXC chemokine from alveolar macrophages

The role of interleukin-8 (IL-8) and related CXC chemokines has been demonstrated in many human diseases. However, more profound studies, e.g., by blocking the effect of these inflammatory mediators, request animal models and hence the identification of all human counterparts for commonly used laboratory animals. In this study, we describe the identification of a novel neutrophil chemotactic protein (NCP) of the rabbit. Intact and NH(2)-terminally truncated NCP forms and IL-8 were isolated from LPS-stimulated rabbit alveolar macrophages and purified to homogeneity by a four-step purification procedure. Determination of the complete primary structure of NCP by mass spectrometry and NH(2)-terminal sequencing of natural protein revealed high structural homology with human epithelial cell-derived neutrophil attractant-78 (ENA-78) and granulocyte chemotactic protein-2 (GCP-2), two related ELR(+)CXC chemokines. Intact NCP(1-76) was found to be 10-fold less potent than truncated NCP(7, 8-76) at inducing neutrophil chemotaxis. NCP(7,8-76) was equally potent as intact rabbit IL-8 at chemoattracting human neutrophils and at inducing calcium fluxes in rabbit neutrophils, 1 ng/mL being the minimal effective concentration. However, like IL-8, NCP failed to induce monocyte or eosinophil migration at 300-fold higher concentrations. IL-8 desensitized the calcium increase induced by NCP and vice versa. Finally, intradermal injection of NCP induced a dose-dependent and significant infiltration of neutrophils in mice skin. It can be concluded that NCP is a novel rabbit CXC chemokine that is, like IL-8, implicated in animal models used to study various human disorders in which neutrophils play an important role.

Regulated production and molecular diversity of human liver and activation-regulated chemokine/macrophage inflammatory protein-3 alpha from normal and transformed cells

Liver and activation-regulated chemokine (LARC), also designated macrophage inflammatory protein-3alpha (MIP-3alpha), Exodus, or CCL20, is a C-C chemokine that attracts immature dendritic cells and memory T lymphocytes, both expressing CCR6. Depending on the cell type, this chemokine was found to be inducible by cytokines (IL-1beta) and by bacterial, viral, or plant products (including LPS, dsRNA, and PMA) as measured by a specific ELISA. Although coinduced with monocyte chemotactic protein-1 (MCP-1) and IL-8 by dsRNA, measles virus, and IL-1beta in diploid fibroblasts, leukocytes produced LARC/MIP-3alpha only in response to LPS. However, in myelomonocytic THP-1 cells LARC/MIP-3alpha was better induced by phorbol ester, whereas in HEp-2 epidermal carcinoma cells IL-1beta was the superior inducer. The production levels of LARC/MIP-3alpha (1-10 ng/ml) were, on the average, 10- to 100-fold lower than those of IL-8 and MCP-1, but were comparable to those of other less abundantly secreted chemokines. Natural LARC/MIP-3alpha protein isolated from stimulated leukocytes or tumor cell lines showed molecular diversity, in that NH(2)- and COOH-terminally truncated forms were purified and identified by amino acid sequence analysis and mass spectrometry. In contrast to other chemokines, including MCP-1 and IL-8, the natural processing did not affect the calcium-mobilizing capacity of LARC/MIP-3alpha through its receptor CCR6. Furthermore, truncated natural LARC/MIP-3alpha isoforms were equally chemotactic for lymphocytes as intact rLARC/MIP-3alpha. It is concluded that in addition to its role in homeostatic trafficking of leukocytes, LARC/MIP-3alpha can function as an inflammatory chemokine during host defense.

Cleavage by CD26/dipeptidyl peptidase IV converts the chemokine LD78beta into a most efficient monocyte attractant and CCR1 agonist

Chemokines are proinflammatory cytokines that play a role in leukocyte migration and activation. Recent reports showed that RANTES (regulated on activation normal T-cell expressed and secreted chemokine), eotaxin, macrophage-derived chemokine (MDC), and stromal cell-derived factor-1 (SDF-1) are NH(2)-terminally truncated by the lymphocyte surface glycoprotein and protease CD26/dipeptidyl peptidase IV (CD26/DPP IV). Removal of the NH(2)-terminal dipeptide resulted in impaired inflammatory properties of RANTES, eotaxin, MDC, and SDF-1. The potential CD26/DPP IV substrate macrophage inflammatory protein-1beta (MIP-1beta) and the related chemokine, LD78alpha (ie, one of the MIP-1alpha isoforms), were not affected by this protease. However, CD26/DPP IV cleaved LD78beta, a most potent CCR5 binding chemokine and inhibitor of macrophage tropic human immunodeficiency virus-1 (HIV-1) infection, into LD78beta(3-70). Naturally truncated LD78beta(3-70), but not truncated MIP-1beta, was recovered as an abundant chemokine form from peripheral blood mononuclear cells. In contrast to all other chemokines processed by CD26/DPP IV, LD78beta(3-70) had increased chemotactic activity in comparison to intact LD78beta. With a minimal effective concentration of 30 pmol/L, LD78beta(3-70) became the most efficient monocyte chemoattractant. LD78beta(3-70) retained its high capacity to induce an intracellular calcium increase in CCR5-transfected cells. Moreover, on CCR1 transfectants, truncated LD78beta(3-70) was 30-fold more potent than intact LD78beta. Thus, CD26/DPP IV can exert not only a negative but also a positive feedback during inflammation by increasing the specific activity of LD78beta. CD26/DPP IV-cleaved LD78beta(3-70) is the most potent CCR1 and CCR5 agonist that retains strong anti-HIV-1 activity, indicating the importance of the chemokine-protease interaction in normal and pathologic conditions. (Blood. 2000;96:1674-1680)

The LD78beta isoform of MIP-1alpha is the most potent CCR5 agonist and HIV-1-inhibiting chemokine

LD78alpha and LD78beta are 2 highly related nonallelic genes that code for different isoforms of the human CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha). Two molecular forms of natural LD78beta (7.778 and 7.793 kDa) were identified from conditioned media of stimulated peripheral blood mononuclear cells. Although LD78alpha and LD78beta only differ in 3 amino acids, both LD78beta variants were 100-fold more potent chemoattractants for mouse lymphocytes than was LD78alpha. On the contrary, LD78beta was only 2-fold more efficient than LD78alpha in chemoattracting human lymphocytes and monocytes. Using CC chemokine receptor-transfected cells, both molecular forms of LD78beta proved to be much more potent than LD78alpha in inducing an intracellular calcium rise through CCR5. Compared with LD78alpha and RANTES, this preferential binding of LD78beta to CCR5 resulted in a 10- to 50-fold higher potency in inhibiting infection of peripheral blood mononuclear cells by CCR5-using (R5) HIV-1 strains. To date, LD78beta is the most potent chemokine for inhibiting HIV-1 infection, and can be considered as a potentially important drug candidate for the treatment of infection with R5 HIV-1 strains.