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.

Diverging binding capacities of natural LD78beta isoforms of macrophage inflammatory protein-1alpha to the CC chemokine receptors 1, 3 and 5 affect their anti-HIV-1 activity and chemotactic potencies for neutrophils and eosinophils

Recently, the LD78beta isoform of the CC chemokine macrophage inflammatory protein (MIP)-1alpha was shown to efficiently chemoattract lymphocytes and monocytes and to inhibit infection of mononuclear cells by R5 HIV-1 strains. We have now demonstrated that after cleavage of the NH2-terminal Ala-Pro dipeptide by CD26, LD78beta(3 - 70) became the most potent chemokine blocking HIV-1. LD78beta(3 - 70) competed tenfold more efficiently than LD78beta(1 - 70) with [125I] RANTES for binding to the CC chemokine receptors CCR5 and CCR1. Contrary to LD78alpha, LD78beta(1 - 70) at 30 ng/ml efficiently competed with [125I] RANTES for binding to CCR3 and mobilized calcium in CCR3 transfectants, whereas LD78beta(3 - 70) showed a 30-fold decrease in CCR3 affinity compared to LD78beta(1 - 70). This demonstrates the importance of the penultimate proline in LD78beta(1 - 70) for CCR3 recognition. Both LD78beta isoforms efficiently chemoattracted eosinophils from responsive donors. In contrast, only the CCR3 agonist LD78beta(1 - 70) and not LD78beta(3 - 70), induced calcium increases in eosinophils with low levels of CCR1. In responder neutrophils, LD78beta(3 - 70) elicited calcium fluxes at a 30-fold lower dose (10 ng/ml) compared to intact LD78beta and LD78alpha, whereas the three MIP-1alpha isoforms were equipotent neutrophil chemoattractants. Taken together, both LD78beta isoforms are potent HIV-1 inhibitors (CCR5) and activators for neutrophils (CCR1) and eosinophils (CCR1, CCR3), affecting infection and inflammation.

Identification of a blood-derived chemoattractant for neutrophils and lymphocytes as a novel CC chemokine, Regakine-1

Chemokines constitute a large family of chemotactic cytokines that selectively attract different blood cell types. Although most inflammatory chemoattractants are only induced and released in the circulation during acute infection, a restricted number of CXC and CC chemokines are constitutively present in normal plasma at high concentrations. Here, such a chemotactic protein was purified to homogeneity from serum and fully identified as a novel CC chemokine by mass spectrometry and amino acid sequence analysis. The protein, tentatively designated Regakine-1, shows less than 50% sequence identity with any known chemokine. This novel CC chemokine chemoattracts both neutrophils and lymphocytes but not monocytes or eosinophils. Its modest chemotactic potency but high blood concentration is similar to that of other chemokines present in the circulation, such as hemofiltrate CC chemokine-1, platelet factor-4, and beta-thromboglobulin. Regakine-1 did not induce neutrophil chemokinesis. However, it synergized with the CXC chemokines interleukin-8 and granulocyte chemotactic protein-2, and the CC chemokine monocyte chemotactic protein-3, resulting in an at least a 2-fold increase of the neutrophil and lymphocyte chemotactic response, respectively. The biologic effects of homogeneous natural Regakine-1 were confirmed with chemically synthesized chemokine. Like other plasma chemokines, it is expected that Regakine-1 plays a unique role in the circulation during normal or pathologic conditions.

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.

NH2- and COOH-terminal truncations of murine granulocyte chemotactic protein-2 augment the in vitro and in vivo neutrophil chemotactic potency

Chemokines are important mediators of leukocyte migration during the inflammatory response. Post-translational modifications affect the biological potency of chemokines. In addition to previously identified NH2-terminally truncated forms, COOH-terminally truncated forms of the CXC chemokine murine granulocyte chemotactic protein-2 (GCP-2) were purified from conditioned medium of stimulated fibroblasts. The truncations generated 28 natural murine GCP-2 isoforms containing 69-92 residues, including most intermediate forms. Both NH2- and COOH-terminal truncations of GCP-2 resulted in enhanced chemotactic potency for human and murine neutrophils in vitro. The truncated isoform GCP-2(9-78) was 30-fold more potent than intact GCP-2(1-92)/LPS-induced CXC chemokine (LIX) at inducing an intracellular calcium increase in human neutrophils. After intradermal injection in mice, GCP-2(9-78) was also more effective than GCP-2(1-92)/LIX at inducing neutrophil infiltration. Similar to human IL-8 and GCP-2, murine GCP-2(9-78) and macrophage inflammatory protein-2 (MIP-2) induced calcium increases in both CXCR1 and CXCR2 transfectants. Murine GCP-2(9-78) could desensitize the calcium response induced by MIP-2 in human neutrophils and vice versa. Furthermore, MIP-2 and truncated GCP-2(9-78), but not intact GCP-2(1-92)/LIX, partially desensitized the calcium response to human IL-8 in human neutrophils. Taken together, these findings point to an important role of post-translationally modified GCP-2 to replace IL-8 in the mouse.

CD26/dipeptidyl-peptidase IV down-regulates the eosinophil chemotactic potency, but not the anti-HIV activity of human eotaxin by affecting its interaction with CC chemokine receptor 3

Chemokines attract and activate distinct sets of leukocytes. The CC chemokine eotaxin has been characterized as an important mediator in allergic reactions because it selectively attracts eosinophils, Th2 lymphocytes, and basophils. Human eotaxin has a penultimate proline, indicating that it might be a substrate for dipeptidyl-peptidase IV (CD26/DPP IV). In this study we demonstrate that eotaxin is efficiently cleaved by CD26/DPP IV and that the NH2-terminal truncation affects its biological activity. CD26/DPP IV-truncated eotaxin(3-74) showed reduced chemotactic activity for eosinophils and impaired binding and signaling properties through the CC chemokine receptor 3. Moreover, eotaxin(3-74) desensitized calcium signaling and inhibited chemotaxis toward intact eotaxin. In addition, HIV-2 infection of CC chemokine receptor 3-transfected cells was inhibited to a similar extent by eotaxin and eotaxin(3-74). Thus, CD26/DPP IV differently regulates the chemotactic and antiviral potencies of eotaxin by the removal of two NH2-terminal residues. This physiological processing may be an important down-regulatory mechanism, limiting eotaxin-mediated inflammatory responses.

Isolation of the CXC chemokines ENA-78, GRO alpha and GRO gamma from tumor cells and leukocytes reveals NH2-terminal heterogeneity. Functional comparison of different natural isoforms

Chemokines are a family of chemotactic peptides affecting leukocyte migration during the inflammatory response. Post-translational modification of chemokines has been shown to affect their biological potency. Here, the isolation and identification of natural isoforms of the neutrophil chemoattractants GRO alpha and GRO gamma and the epithelial-cell-derived neutrophil attractant-78 (ENA-78), is reported. Cultured tumor cells produced predominantly intact chemokine forms, whereas peripheral blood monocytes secreted mainly NH2-terminally truncated forms. The order of neutrophil chemotactic potency of these CXC chemokines was GRO alpha > GRO gamma > ENA-78 both for intact and truncated forms. However, truncated GRO alpha (4,5,6-73), GRO gamma (5-73) and ENA-78(8,9-78) were 30-fold, fivefold and threefold more active than the corresponding intact chemokine. As a consequence, truncated GRO alpha (4,5,6-73) was 300-fold more potent than intact ENA-78 indicating that both the type of chemokine and its mode of processing determine the chemotactic potency. Similar observations were made when intact and truncated GRO alpha, GRO gamma and ENA-78 were compared for their capacity to induce an increase in the intracellular calcium concentration in neutrophilic granulocytes, and to desensitize the calcium response towards the CXC chemokine granulocyte chemotactic protein-2 (GCP-2). It must be concluded that physiological proteolytic cleavage of CXC chemokines in general enhances the inflammatory response, whereas for CC chemokines NH2-terminal processing mostly results in reduced chemotactic potency.

Differential induction of monocyte chemotactic protein-3 in mononuclear leukocytes and fibroblasts by interferon-alpha/beta and interferon-gamma reveals MCP-3 heterogeneity

Monocyte chemotactic protein-3 (MCP-3) is a pluripotent CC chemokine, attracting most leukocytic cell types. With the use of a sensitive and specific ELISA, MCP-3 was found to be inducible in fibroblasts and peripheral blood mononuclear cells (PBMC) by cytokines and cytokine inducers. MCP-3 production levels (1-10 ng/ml) were tenfold lower compared to those of MCP-1. In diploid fibroblasts, synergistic induction of MCP-3, but not of MCP-1, mRNA and protein was observed by combined treatment with IL-1beta and IFN-gamma. In PBMC, IFN-alpha and IFN-beta (but not IFN-gamma), as well as measles virus and double-stranded RNA, were potent inducers of MCP-3, which suggests a role for this chemokine in an early stage of viral infections. In contrast, endotoxin failed to induce MCP-3 production in fibroblasts and PBMC. Purification of MCP-3 from PBMC revealed biochemical heterogeneity. In monocyte chemotaxis and calcium mobilization assays, pure 11-kDa MCP-3 from PBMC showed similar potencies as MCP-3 from tumor cells. It was concluded that the induction of MCP-3 by IFN is regulated differently in fibroblasts and PBMC. In view of the multiple target cells for MCP-3, local and strictly regulated chemokine production might be important to conduct selectively the immune response in infection or inflammation.

Processing by CD26/dipeptidyl-peptidase IV reduces the chemotactic and anti-HIV-1 activity of stromal-cell-derived factor-1alpha

The chemokine stromal-cell-derived factor-1alpha (SDF-1alpha) chemoattracts lymphocytes and CD34+ haematopoietic progenitors and is the ligand for CXCR4 (CXC chemokine receptor 4), the main co-receptor for T-tropic HIV-1 strains. SDF-1alpha was NH2-terminally cleaved to SDF-1alpha(3-68) by dipeptidyl-peptidase IV (CD26/DPP IV), which is present in blood in soluble and membrane-bound form. SDF-1alpha(3-68) lost both lymphocyte chemotactic and CXCR4-signaling properties. However, SDF-1alpha(3-68) still desensitized the SDF-1alpha(1-68)-induced Ca2+ response. In contrast to CD26/DPP IV-processed RANTES(3-68), SDF-1alpha(3-68) had diminished potency to inhibit HIV-1 infection. Thus, CD26/DPP IV impairs the inflammatory and haematopoietic potency of chemokines but plays a dual role in AIDS.

Differential usage of the CXC chemokine receptors 1 and 2 by interleukin-8, granulocyte chemotactic protein-2 and epithelial-cell-derived neutrophil attractant-78

The inflammatory response is mediated by a family of chemotactic cytokines, designated chemokines. The receptor usage of the CXC chemokine granulocyte chemotactic protein-2 (GCP-2) was compared with that of interleukin-8 (IL-8) and epithelial-cell-derived neutrophil attractant-78 (ENA-78). Chemokine activities were evaluated by measurement of intracellular calcium increase and by chemotaxis and binding assays, using CXC chemokine receptor (CXCR)-transfected cell lines. GCP-2 was equally potent at inducing a rise in [Ca2+]i in both CXCR1-transfected and CXCR2-transfected cells (minimal effective concentration 3 nM). IL-8 augmented the [Ca2+]i more efficiently in CXCR1-transfectants than in CXCR2-transfectants, whereas for ENA-78, threefold higher concentrations were necessary to obtain a calcium response in CXCR1-transfected cells than in CXCR2-transfectants. GCP-2 desensitized the calcium increase induced by IL-8 in both CXCR1-transfected and CXCR2-transfected cells, but ENA-78 only affected the IL-8-induced calcium response in CXCR2-transfectants. The half-maximal effective concentrations for migration of CXCR2-transfectants in response to GCP-2 and ENA-78 were similar (0.1 nM), whereas GCP-2 was tenfold more potent than ENA-78 on CXCR1-transfectants. Half-maximal migration of CXCR1-transfected and CXCR2-transfected cells was obtained with IL-8 at concentrations of no more than 0.01 nM. Radiolabeled IL-8 could efficiently be displaced from CXCR2 by IL-8, GCP-2 and ENA-78. In contrast, only IL-8 and GCP-2 but not ENA-78, competed for 125I-IL-8 binding to CXCR1. From these data, it can be concluded that, in addition to IL-8, GCP-2, but not ENA-78, efficiently binds to both CXCR1 and CXCR2. The differential receptor usage of the structurally related ELR+ CXC chemokines GCP-2 and ENA-78 is indicative of a different role in inflammatory reactions.

Posttranslational modifications affect the activity of the human monocyte chemotactic proteins MCP-1 and MCP-2: identification of MCP-2(6-76) as a natural chemokine inhibitor

Chemokines are important mediators in infection and inflammation. The monocyte chemotactic proteins (MCPs) form a subclass of structurally related C-C chemokines. MCPs select specific target cells due to binding to a distinct set of chemokine receptors. Recombinant and synthetic MCP-1 variants have been shown to function as chemokine antagonists. In this study, posttranslationally modified immunoreactive MCP-1 and MCP-2 were isolated from mononuclear cells. Natural forms of MCP-1 and MCP-2 were biochemically identified by Edman degradation and mass spectrometry and functionally characterized in chemotaxis and Ca2+-mobilization assays. Glycosylated MCP-1 (12 and 13.5 kDa) was found to be two- to threefold less chemotactic for monocytes and THP-1 cells than nonglycosylated MCP-1 (10 kDa). Natural, NH2-terminally truncated MCP-1(5-76) and MCP-1(6-76) were practically devoid of bioactivity, whereas COOH-terminally processed MCP-1(1-69) fully retained its chemotactic and Ca2+-inducing capacity. The capability of naturally modified MCP-1 forms to desensitize the Ca2+ response induced by intact MCP-1 in THP-1 cells correlated with their agonistic potency. In contrast, naturally modified MCP-2(6-76) was devoid of activity, but could completely block the chemotactic effect of intact MCP-2 as well as that of MCP-1, MCP-3, and RANTES. Carboxyl-terminally processed MCP-2(1-74) did retain its chemotactic potency. Although comparable as a chemoattractant, natural intact MCP-2 was found to be 10-fold less potent than MCP-1 in inducing an intracellular Ca2+ increase. It can be concluded that under physiologic or pathologic conditions, posttranslational modification affects chemokine potency and that natural MCP-2(6-76) is a functional C-C chemokine inhibitor that might be useful as an inhibitor of inflammation.

Natural truncation of RANTES abolishes signaling through the CC chemokine receptors CCR1 and CCR3, impairs its chemotactic potency and generates a CC chemokine inhibitor

Selective leukocyte trafficking towards sites of inflammation is mediated by chemokines. RANTES is a CC chemokine that attracts lymphocytes, monocytes, dendritic cells, eosinophils, basophils and NK cells. A natural form of human RANTES lacking two N-terminal residues was isolated from stimulated sarcoma cells, fibroblasts, and leukocytes. RANTES(3-68) showed a more than tenfold reduction in chemotactic potency for monocytes and eosinophils. To elucidate the mechanism involved, receptor recognition studies were performed. In cells transfected with the CC chemokine receptor (CCR) 5, the major co-receptor for macrophage-tropic HIV-1 strains, RANTES(3-68) mobilized calcium and desensitized RANTES(1-68)-induced calcium fluxes equally well as RANTES(1-68). However, RANTES(3-68) was ineffective on CCR1 and CCR3 transfectants. The reduced potency of natural RANTES(3-68) by selective loss of receptor-activating characteristics was confirmed with recombinant RANTES(3-68). In chemotaxis assays using monocytic cells, RANTES(3-68) inhibited RANTES(1-68), macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta or monocyte chemotactic protein-3 (MCP-3), but not MCP-1- or MCP-2-induced chemotaxis. Thus, a minor post-translational modification has a remarkable impact on the biological activities of RANTES and a pathophysiologically induced change in the relative amounts of intact and truncated RANTES might affect the outcome of inflammation or HIV infection.

Synergistic induction of MCP-1 and -2 by IL-1beta and interferons in fibroblasts and epithelial cells

Monocyte chemotactic protein (MCP)-1 and MCP-2, two closely related CC chemokines, are important mediators of monocyte and lymphocyte migration. These chemokines are secreted by various normal cell types, including fibroblasts, epithelial cells, and leukocytes, as well as by tumor cells. After stimulation with different cytokines and cytokine inducers the MCP-2 production levels are always lower than those of MCP-1. In human diploid fibroblasts cytokines differentially regulate chemokine induction, interleukin (IL)-1beta and interferon (IFN)-gamma being potent stimuli of MCP-1 and MCP-2, respectively. Co-stimulation of fibroblasts by 10 U/mL IL-1beta and 20 ng/mL IFN-gamma resulted in a synergistic induction of MCP-2, whereas the combined effect on MCP-1 and IL-6 production was rather additive. These findings were confirmed at the mRNA level by Northern blot analysis. In contrast, in human MG-63 fibroblastoid cells and HEp-2 epithelial cells, selected for their poor responsiveness to IL-1beta and IFN-gamma, MCP-2 as well as MCP-1 and IL-6 were synergistically induced, yielding protein levels that were increased 3- to 30-fold above the additive levels. When IFN-beta was used as a co-stimulant of IL-1beta, a similar synergistic induction of MCP-1 and MCP-2 was measured both at the protein and the mRNA level. It can be concluded that, when synergy occurred, the MCP-1 and MCP-2 expression levels reached a comparable maximum, indicative for an equal contribution of these chemokines in normal and pathological conditions.

Identification of mouse granulocyte chemotactic protein-2 from fibroblasts and epithelial cells. Functional comparison with natural KC and macrophage inflammatory protein-2

Neutrophil and monocyte chemotactic factors were isolated from conditioned media of mouse fibroblasts and epithelial cells. Neutrophil chemotactic activities were purified to homogeneity using a four-step chromatographic procedure, and the corresponding proteins were identified by amino acid sequence analysis. Natural forms of the murine chemokines KC and macrophage inflammatory protein-2 were isolated from virus-infected fibroblasts. However, the major neutrophil chemotactic activity from fibroblasts stimulated with endotoxin plus double-stranded RNA and from PMA-treated epithelial cells resided in other 7- and 8-kDa proteins. Amino acid sequence analysis revealed a novel Cys-Xaa-Cys chemokine structure, characterized by the conservation of four cysteines and the Glu-Leu-Arg motif. Based on the completely identified primary structure of this natural protein, this chemokine must be considered to be the murine homologue of human and bovine granulocyte chemotactic protein-2 (GCP-2; 61 and 64% identical residues, respectively). Due to NH2-terminal cleavage, 11 different forms of mouse GCP-2 were discovered. In contrast to human and bovine GCP-2, functional comparison of long and short NH2-terminal forms of mouse GCP-2 demonstrated that truncated mouse GCP-2 (short form) has a higher specific activity in neutrophil activation (gelatinase B release) and chemotaxis assays. Furthermore, mouse GCP-2 was more potent than human GCP-2 on human neutrophils, and more active than murine KC and macrophage inflammatory protein-2 on mouse neutrophils. In view of the absence of a murine homologue for IL-8, NH2-terminally processed GCP-2 can be considered a major neutrophil chemoattractant in the mouse during the inflammatory response.

Identification of mouse granulocyte chemotactic protein-2 from fibroblasts and epithelial cells. Functional comparison with natural KC and macrophage inflammatory protein-2

Neutrophil and monocyte chemotactic factors were isolated from conditioned media of mouse fibroblasts and epithelial cells. Neutrophil chemotactic activities were purified to homogeneity using a four-step chromatographic procedure, and the corresponding proteins were identified by amino acid sequence analysis. Natural forms of the murine chemokines KC and macrophage inflammatory protein-2 were isolated from virus-infected fibroblasts. However, the major neutrophil chemotactic activity from fibroblasts stimulated with endotoxin plus double-stranded RNA and from PMA-treated epithelial cells resided in other 7- and 8-kDa proteins. Amino acid sequence analysis revealed a novel Cys-Xaa-Cys chemokine structure, characterized by the conservation of four cysteines and the Glu-Leu-Arg motif. Based on the completely identified primary structure of this natural protein, this chemokine must be considered to be the murine homologue of human and bovine granulocyte chemotactic protein-2 (GCP-2; 61 and 64% identical residues, respectively). Due to NH2-terminal cleavage, 11 different forms of mouse GCP-2 were discovered. In contrast to human and bovine GCP-2, functional comparison of long and short NH2-terminal forms of mouse GCP-2 demonstrated that truncated mouse GCP-2 (short form) has a higher specific activity in neutrophil activation (gelatinase B release) and chemotaxis assays. Furthermore, mouse GCP-2 was more potent than human GCP-2 on human neutrophils, and more active than murine KC and macrophage inflammatory protein-2 on mouse neutrophils. In view of the absence of a murine homologue for IL-8, NH2-terminally processed GCP-2 can be considered a major neutrophil chemoattractant in the mouse during the inflammatory response.

Purification and Identification of Natural Chemokines

A novel family of chemotactic cytokines or chemokines, essential for the directed migration of leukocytes to sites of inflammation, has been identified during the past decade. To obtain microgram amounts of natural chemokines, normal (e.g., freshly isolated leukocytes, connective tissue cell cultures) or malignant cell lines have to be selectively induced with endogenous (cytokines) or exogenous (bacterial, viral, or plant) products. We have developed a four-step procedure that allows for the complete purification of active C-C (MCP-1, MCP-2, MCP-3, RANTES, MIP-1alpha and MIP-1beta) and C-X-C (IL-8, GRO-alpha, GRO-beta, GRO-gamma, GCP-2, ENA-78, IP-10, PF-4, and CTAPIII/betaTG/NAP-2) chemokines from bulk volumes of culture supernatant. This method is applicable for the isolation of recombinant chemokines. Conditioned medium was first concentrated and partially purified on silicic acid or controlled pore glass beads. Further purification to homogeneity was achieved using heparin-Sepharose or antibody affinity chromatography, cation exchange FPLC, and reverse-phase HPLC. Purification of chemokines was monitored by testing column fractions for biological (chemotaxis) or immuno (RIA, ELISA) activity and protein content (SDS-PAGE). Homogeneous proteins were identified by amino-terminal or internal protein sequence analysis.

Purification, sequence analysis, and biological characterization of a second bovine monocyte chemotactic protein-1 (Bo MCP-1B)

Madin Darby bovine kidney (MDBK) cells were used as a source to identify novel bovine chemotactic factors for granulocytes and monocytes. A major bovine granulocyte chemotactic protein (GCP-2) has previously been isolated. A novel bovine monocyte chemotactic protein (bo MCP) was produced on MDBK cells stimulated with phorbol ester. The 14-kDa protein was purified to homogeneity by adsorption to controlled pore glass, heparin affinity chromatography, cation-exchange FPLC, and RP-HPLC. The amino acid sequence of the NH2-terminally blocked protein was determined by Edman degradation using proteolytic fragments. The primary structure of the bo MCP, characterized by four conserved cysteines, allowed classification of the protein within the C-C chemokine family. Bo MCP-1B was most related to known human and bovine MCPs. Compared to bovine MCP-1 and MCP-2, the protein consists of 84% and 53% identical amino acids, respectively. Since this bo MCP was also most homologous to human and animal MCP-1, it was designated bo MCP-1B. The minimal effective dose of bo MCP-1B for monocyte chemotactic activity was 0.2 mM. The maximal migration index, reached at 2 nM, was comparable to that of natural human MCP-1. Furthermore, bo MCP-1B was found to be capable of stimulating beta-glucuronidase release from monocytes. In contrast, bo MCP-1B was not chemotactic for neutrophilic and eosinophilic granulocytes. By its biological and biochemical characteristics, bo MCP-1B has to be considered as an authentic additional MCP-1 chemokine. The existence of a possible human counterpart for this novel MCP-1B still needs to be elucidated.

Leukocyte recruitment by monocyte chemotactic proteins (MCPs) secreted by human phagocytes

Phagocyte recruitment is an important immunological phenomenon in inflammation and cancer. A large family of selective chemotactic cytokines, designated chemokines, has recently emerged. Interleukin-8 (IL-8) is the prototype of such neutrophil activating factors, whereas MCP-1 is a well studied monocyte chemotactic protein. In vitro chemotactic assays were used to isolate and identify natural chemokines from mononuclear phagocytes and tumor cells. Additional new chemotactic proteins (MCP-2, MCP-3) attracting monocytes were also discovered by these methods. All chemokines are structurally related and show affinity for heparin. MCP-1, -2 and -3 have a comparable specific activity in monocyte chemotaxis assays. Specific and sensitive radioimmunoassays for MCP-1 and IL-8 were developed to study the regulation of their secretion by leukocytes. Monocytes or monocyte tumor cells produce MCP-1 and/or IL-8 in response to cytokines, virus, double stranded RNA, bacterial endotoxin, mitogen or phorbol ester. Granulocytes were found to secrete only minor amounts of MCP-1 and IL-8.

Induction of monocyte chemotactic proteins MCP-1 and MCP-2 in human fibroblasts and leukocytes by cytokines and cytokine inducers. Chemical synthesis of MCP-2 and development of a specific RIA

Monocyte chemotactic proteins (MCP) belong to a group of structurally and functionally related factors, called chemokines. To facilitate additional characterization of the recently identified MCP-2, the 76-residue protein was chemically synthesized. The synthetic 7-kDa monomeric protein was chemotactic for monocytes at 1 nM and was biochemically similar to natural MCP-2. Sensitive radioimmunoassays for both MCP-1 and MCP-2 were developed. These RIAs were specific in that no cross-reactivity could be observed, and other chemokines or cytokines were not detected. Induction of MCP-1 and MCP-2 in human diploid fibroblasts and peripheral blood leukocytes as well as osteosarcoma, epidermal carcinoma, and melanoma cells by the cytokines IL-1 beta, IFN-beta, and IFN-gamma and cytokine inducers such as dsRNA, virus, endotoxin, mitogen, and phorbol ester was studied. In connective tissue cells, IL-1 beta was the best inducer of MCP-1, but IFN-gamma was a superior inducer of MCP-2. Mononuclear cells also proved to be a source of MCP-1 and MCP-2 when stimulated by most of the inducers tested. Granulocytes, however, were inefficient producers. Measles virus induced MCP-1 and MCP-2 in most cell types. In general, the yields of MCP-2 were at least 10-fold lower than those of MCP-1. It is concluded that, although MCP-2 is often coproduced with MCP-1, regulation of expression of the two chemokines is not identical. It remains to be studied under which pathological conditions MCP-2 is released in vivo and whether MCP-1 and MCP-2 can activate different target cells.

Induction of monocyte chemotactic proteins MCP-1 and MCP-2 in human fibroblasts and leukocytes by cytokines and cytokine inducers. Chemical synthesis of MCP-2 and development of a specific RIA

Monocyte chemotactic proteins (MCP) belong to a group of structurally and functionally related factors, called chemokines. To facilitate additional characterization of the recently identified MCP-2, the 76-residue protein was chemically synthesized. The synthetic 7-kDa monomeric protein was chemotactic for monocytes at 1 nM and was biochemically similar to natural MCP-2. Sensitive radioimmunoassays for both MCP-1 and MCP-2 were developed. These RIAs were specific in that no cross-reactivity could be observed, and other chemokines or cytokines were not detected. Induction of MCP-1 and MCP-2 in human diploid fibroblasts and peripheral blood leukocytes as well as osteosarcoma, epidermal carcinoma, and melanoma cells by the cytokines IL-1 beta, IFN-beta, and IFN-gamma and cytokine inducers such as dsRNA, virus, endotoxin, mitogen, and phorbol ester was studied. In connective tissue cells, IL-1 beta was the best inducer of MCP-1, but IFN-gamma was a superior inducer of MCP-2. Mononuclear cells also proved to be a source of MCP-1 and MCP-2 when stimulated by most of the inducers tested. Granulocytes, however, were inefficient producers. Measles virus induced MCP-1 and MCP-2 in most cell types. In general, the yields of MCP-2 were at least 10-fold lower than those of MCP-1. It is concluded that, although MCP-2 is often coproduced with MCP-1, regulation of expression of the two chemokines is not identical. It remains to be studied under which pathological conditions MCP-2 is released in vivo and whether MCP-1 and MCP-2 can activate different target cells.

Human and bovine granulocyte chemotactic protein-2: complete amino acid sequence and functional characterization as chemokines

Tumor cells are capable of simultaneously producing a number of related inflammatory peptides, now classified as chemokines. We have isolated a new human granulocyte chemotactic protein (GCP-2), coproduced with interleukin-8 (GCP-1/IL-8) by osteosarcoma cells. Furthermore, the bovine homologue of human GCP-2 was purified from kidney tumor cells using the same isolation procedure. Both chemokines occur in at least four NH2-terminally truncated forms. These 5-6 kDa proteins do not differ in potency and efficacy as granulocyte chemotactic factors using a standard in vitro migration assay. The complete primary structures of human and bovine GCP-2 were disclosed by sequencing peptide fragments derived from the natural proteins. On the basis of the conservation of four cysteine residues, the two molecules are to be classified within the C-X-C chemokine family, including IL-8. Human and bovine GCP-2 are 67% similar at the amino acid level. Their sequences show only weak similarity with that of IL-8, and human GCP-2 does not cross-react in a radioimmunoassay for IL-8. Human and bovine GCP-2 are specific granulocyte chemotactic factors in that they do not attract human monocytes. Bovine GCP-2 is not species specific since it is at least as active as human GCP-2 on human granulocytes. Both chemokines can also activate postreceptor mechanisms leading to release of gelatinase B by granulocytes. This is indicative for a possible role in inflammation and tumor cell invasion.

Structural and functional identification of two human, tumor-derived monocyte chemotactic proteins (MCP-2 and MCP-3) belonging to the chemokine family

Cytokine-stimulated human osteosarcoma cells (MG-63) secrete several related chemotactic factors, including the neutrophil-activating protein interleukin 8 (IL-8) and the monocyte chemotactic protein (MCP)-1. We describe the isolation and characterization of two novel monocyte chemotactic factors from this tumor cell line. Although these proteins copurified with MCP-1 and IL-8 on heparin-Sepharose, they could be separated by cation-exchange fast protein liquid chromatography and reverse-phase high-performance liquid chromatography. The corresponding 7.5- and 11-kD proteins were NH2-terminally blocked but were identified by sequencing peptide fragments. They showed a primary structure mostly related to that of MCP-1 and were therefore designated MCP-2 and MCP-3, respectively. These molecules can be classified in a subfamily of proinflammatory proteins characterized by the conservation of cysteine residues. MCP-2 and MCP-3 are also functionally related to MCP-1 because they specifically attract monocytes, but not neutrophils, in vitro. The chemotactic potency (specific activity) was comparable for all three MCPs. Intradermal injection of these proteins in rabbits resulted in selective monocyte recruitment in vivo. Since tumor cells are good producers of leukocyte chemotactic factors, it could be questioned whether these molecules can indirectly control tumor growth by attracting leukocytes or whether they rather promote invasion by the secretion of proteases from the attracted cells.

Bradykinin induces interleukin-6 and synergizes with interleukin-1

Bradykinin was found to induce production of IL-6 in human diploid fibroblasts, as well as in a hepatoma-derived cell line, but not in a human melanoma or an osteosarcoma cell line. With the exception of the melanoma cell line, these cells were also found to be responsive to IL-1 beta. The response to bradykinin was faster but less high than that induced by IL-1. Experiments in which IL-1 (-alpha or -beta) and bradykinin were applied simultaneously revealed a synergistic interaction. Of the other cytokines tested, TNF-alpha and IFN-gamma weakly induced IL-6. Neither IL-2, IFN-alpha, nor IFN-beta was able to induce IL-6, either in the absence or the presence of bradykinin. These observations constitute further evidence for the existence of interactions between cytokine and noncytokine peptides, thus linking the neuroendocrine and immune systems.

Production and identification of natural monocyte chemotactic protein from virally infected murine fibroblasts. Relationship with the product of the mouse competence (JE) gene

Primary cultures of mouse embryonic fibroblasts and confluent monolayers of mouse fibroblastoid cells (L929) were found to secrete a chemotactic factor specific for monocytes. It biological activity was deduced from both the migration distance under agarose and the number of migrated monocytes in the micropore filter method. The monocyte chemotactic protein (MCP) was inducible in these cells by double-stranded RNA and by infection with virus. In embryonic fibroblasts MCP was also produced in response to the cytokines interleukin-1 (IL-1) and tumor necrosis factor (TNF). Under all conditions for induction of MCP tested no production of chemotactic activity for granulocytes could be detected. MCP activity from virally infected L929 cells was concentrated and purified by sequential adsorption to controlled pore glass, heparin-Sepharose chromatography, ion-exchange FPLC and reversed-phase HPLC. Pure MCP was found to occur mainly as a 7-8-kDa protein. Although the mature protein possessed a blocked NH2-terminus, it was identified by enzymatic cleavage and sequence analysis of an internal fragment. The sequence obtained corresponded to a part of the cDNA-derived protein sequence of the murine 'competence' (JE) gene, inducible in fibroblasts by cytokines and virus. In all probability the 7-8-kDa MCP form represents the natural product of the mouse gene JE. Murine MCP can thus be classified in the novel family of small inducible inflammatory proteins.

Identification of the monocyte chemotactic protein from human osteosarcoma cells and monocytes: detection of a novel N-terminally processed form

The chemotactic activity for monocytes in culture supernatants from double-stranded RNA-stimulated human MG-63 osteosarcoma cells and from LPS-stimulated human monocytes was purified to homogeneity and characterized by amino acid sequence analysis. The chemotactic protein derived from the fibroblastoid osteosarcoma cells had a blocked N-terminus but sequencing of tryptic fragments showed that it was identical with a recently identified monocyte chemoattractant designated MCP-1 or MCAF isolated from glioma or myelomonocytic cells, respectively. Preparations of monocyte -derived chemotactic activity appeared to contain not only the blocked protein, but also a novel N-terminally processed form of this molecule, lacking 5 amino acid residues.

Identification by sequence analysis of chemotactic factors for monocytes produced by normal and transformed cells stimulated with virus, double-stranded RNA or cytokine

A monocyte chemotactic activity was found to be released by various types of cultured human cells after appropriate stimulation: normal diploid fibroblasts, peripheral blood mononuclear cells or monocytes isolated therefrom, and a number of tumor cell lines, including osteosarcoma (MG-63) and hepatoma (Malavu) but not melanoma (Bowes) cells. Cultures of diploid human fibroblasts and these tumor cells stimulated with interleukin (IL) 1 or double-stranded RNA [poly(rI).poly(rC)], or infected with viruses (measles or rubella viruses) were found to produce chemotactic activity for both monocytes and granulocytes. Media collected from fibroblasts treated with E. coli or IL 6 did not contain such activity. Granulocyte and monocyte chemotactic activities were serologically distinct, and could be separated by successive chromatographical procedures. While the granulocyte chemotactic activity of both fibroblasts and MG-63 cells had previously been identified as granulocyte chemotactic protein/IL 8, the monocyte chemotactic activity from MG-63 cells was identified by amino acid sequence analysis as a different protein recently described to be released by human glioma and myelomonocytic cell lines. In view of the similarity in their chromatographical behavior, monocyte chemotactic activities from fibroblasts, MG-63 cells and fresh monocytes can probably be assigned to identical molecules. Cultures of unfractionated peripheral blood cells, however, were found to release an additional monocyte chemotactic protein, identifiable by amino acid sequence analysis as platelet factor 4.

The chemotactic activity for granulocytes produced by virally infected fibroblasts is identical to monocyte-derived interleukin 8

So far, the role of fibroblasts in inflammatory processes has been underestimated. We have previously shown that stimulation of fibroblasts with viruses or bacteria results in a simultaneous production of several cytokines, including interferon-beta, interleukin (IL) 6 and colony-stimulating factors. We here report that virally infected fibroblasts produce also a chemotactic factor for granulocytes. The activity is inducible not only by measles virus but also by IL 1 beta and the double-stranded RNA poly(rI).poly(rC). This factor, when purified to homogeneity, occurs as a 6-7-kDa protein doublet upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pure protein is serologically related to a fully characterized granulocyte chemotactic peptide (GCP) from monocytes, designated IL8. Furthermore, the chemotactic factor from fibroblasts has an NH2-terminal sequence identical to that of GCP/IL8, small differences in NH2-terminal processing being observed. Finally, in addition to diploid fibroblasts, the osteosarcoma MG-63 cell line is also a producer of GCP/IL8. It can thus be concluded that GCP/IL8 can be produced by several cell types in response to infection and that fibroblasts can contribute to chemotaxis in inflammation.

Purification and characterization of human fibroblast-derived hybridoma growth factor identical to T-cell-derived B-cell stimulatory factor-2 (interleukin-6)

Human fibroblast cultures, when stimulated with interleukin-1 (IL-1) produce a growth factor for B-cell hybridoma and plasmocytoma cell lines. The availability of both a fast-growing and high-producer cell line (MG-63 osteosarcoma cells) and of a highly sensitive and specific assay system for this hybridoma growth factor (HGF) allowed us to obtain analytically pure preparations. Crude HGF from MG-63 cells was processed through a five-step concentration and purification schedule. Sequential adsorption to controlled pore glass (CPG) beads, antibody affinity chromatography and gel filtration resulted in a 10,000-fold purification to a specific activity of 10(9) units/mg HGF. Electrophoretically pure HGF was obtained after additional purification by cation-exchange chromatography and reversed-phase HPLC. The purification procedure revealed two distinct biologically active HGF components. The amino-terminal sequence of one of the two components was determined and found to correspond to that already predicted from cDNA clones of a protein alternatively called 26-kDa protein, interferon-beta 2 (IFN-beta 2) or B-cell stimulating factor-2 (BSF-2). The first two designations (26-kDa protein and IFN-beta 2) refer to a postulated fibroblast secretory protein with so far no unambiguously defined function; the latter designation (BSF-2) refers to a T-cell product possessing differentiation stimulatory effect on B-cell lines. The reported results firmly establish that the protein is secreted by fibroblasts and reveal that it possesses B-cell growth stimulatory activity. The new designation interleukin-6 (IL-6) is proposed to resolve prescribing nomenclature confusion.