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

Chemokine isoforms and processing in inflammation and immunity

The first dimension of chemokine heterogeneity is reflected by their discovery and purification as natural proteins. Each of those chemokines attracted a specific inflammatory leukocyte type. With the introduction of genomic technologies, a second wave of chemokine heterogeneity was established by the discovery of putative chemokine-like sequences and by demonstrating chemotactic activity of the gene products in physiological leukocyte homing. In the postgenomic era, the third dimension of chemokine heterogeneity is the description of posttranslational modifications on most chemokines. Proteolysis of chemokines, for instance by dipeptidyl peptidase IV (DPP IV/CD26) and by matrix metalloproteinases (MMPs) is already well established as a biological control mechanism to activate, potentiate, dampen or abrogate chemokine activities. Other posttranslational modifications are less known. Theoretical N-linked and O-linked attachment sites for chemokine glycosylation were searched with bio-informatic tools and it was found that most chemokines are not glycosylated. These findings are corroborated with a low number of experimental studies demonstrating N- or O-glycosylation of natural chemokine ligands. Because attached oligosaccharides protect proteins against proteolytic degradation, their absence may explain the fast turnover of chemokines in the protease-rich environments of infection and inflammation. All chemokines interact with G protein-coupled receptors (GPCRs) and glycosaminoglycans (GAGs). Whether lectin-like GAG-binding induces cellular signaling is not clear, but these interactions are important for leukocyte migration and have already been exploited to reduce inflammation. In addition to selective proteolysis, citrullination and nitration/nitrosylation are being added as biologically relevant modifications contributing to functional chemokine heterogeneity. Resulting chemokine isoforms with reduced affinity for GPCRs reduce leukocyte migration in various models of inflammation. Here, these third dimension modifications are compared, with reflections on the biological and pathological contexts in which these posttranslational modifications take place and contribute to the repertoire of chemokine functions and with an emphasis on autoimmune diseases.

Effect of posttranslational processing on the in vitro and in vivo activity of chemokines

The CXC and CC chemokine gene clusters provide an abundant number of chemotactic factors selectively binding to shared G protein-coupled receptors (GPCR). Hence, chemokines function in a complex network to mediate migration of the various leukocyte subsets, expressing specific GPCRs during the immune response. Further fine-tuning of the chemokine system is reached through specific posttranslational modifications of the mature proteins. Indeed, enzymatic processing of chemokines during an early phase of inflammation leads to activation of precursor molecules or cleavage into even more active or receptor specific chemokine isoforms. At a further stage, proteolytic processing leads to loss of GPCR signaling, thereby providing natural chemokine receptor antagonists. Finally, further NH(2)-terminal cleavage results in complete inactivation to dampen the inflammatory response. During inflammatory responses, the two chemokines which exist in a membrane-bound form may be released by proteases from the cellular surface. In addition to proteolytic processing, citrullination and glycosylation of chemokines is also important for their biological activity. In particular, citrullination of arginine residues seems to reduce the inflammatory activity of chemokines in vivo. This goes along with other positive and negative regulatory mechanisms for leukocyte migration, such as chemokine synergy and scavenging by decoy receptors.

Herpes simplex virus and the chemokines that mediate the inflammation

Herpes simplex viruses (HSV) are highly pervasive pathogens in the human host with a seroconversion rate upwards of 60% worldwide. HSV type 1 (HSV-1) is associated with the disease herpetic stromal keratitis, the leading cause of infectious corneal blindness in the industrialized world. Individuals suffering from genital herpes associated with HSV type 2 (HSV-2) are found to be two- to threefold more susceptible in acquiring human immunodeficiency virus (HIV). The morbidity associated with these infections is principally due to the inflammatory response, the development of lesions, and scarring. Chemokines have become an important aspect in understanding the host immune response to microbial pathogens due in part to the timing of expression. In this paper, we will explore the current understanding of chemokine production as it relates to the orchestration of the immune response to HSV infection.

Effects of dietary omega3 and omega6 lipids and vitamin E on chemokine levels in autoimmune-prone MRL/MpJ-lpr/lpr mice

Elevated levels of chemokines, such as Regulated upon Activation, Normal T cell Expressed and Secreted (RANTES), Monocyte Chemotactic Protein-1 (MCP-1), Macrophage Inflammatory Protein-1alpha (MIP-1alpha), and Macrophage Inflammatory Protein-1beta (MIP-1beta) have been found in rheumatoid arthritis (RA) and juvenile arthritis (JA), and they may be associated with the pathogenesis of these diseases. These chemokines are implicated in the migration of specific leukocytes into the joints. Omega-3 (omega3) fatty acid rich-fish oil (FO) and vitamin E may delay the progress of certain autoimmune diseases. The present study was designed to understand the effects of dietary lipids (omega-6 and omega-3 fatty acids) and vitamin E on the production of chemokines in autoimmune-prone MRL/lpr (a mouse model for RA) and congenic control MRL/++ mice. The MRL mice were fed for 4.5 months omega-6 and omega-3 diets that varied in lipid sources (corn oil; CO and fish oil; FO) and vitamin E levels (269 I.U./kg and 694 I.U./kg diet). Spleen cells were isolated and cultured aseptically in the presence of PHA for 48 h at 37 degrees C and the levels of chemokines (RANTES, JE/MCP-1 and MIP-1alpha) were determined in the cell-free supernatants. The levels of RANTES and JE/MCP-1 were significantly higher in MRL/lpr mice compared to MRL/++ mice. The FO had differential effect on RANTES and MCP-1 production by spleen cells. The production of RANTES and JE/MCP-1 by spleen cells in mice fed the FO diets was significantly lower than in mice fed the CO diets (p < 0.0001). The levels of vitamin E did not affect the production of RANTES and JE/MCP-1. The levels of vitamin E had a significant effect on MIP-1alpha as the spleen cells of mice fed diets containing 694 IU/kg diet of vitamin E produced significantly higher levels of MIP-1alpha compared to the group of mice fed the diets containing 269 IU of vitamin E (p < 0.0001). The data obtained from this study in MRL/lpr and MRL/++ mice suggest that FO diets containing omega-3 fatty acids are beneficial in decreasing the levels of certain pro-inflammatory chemokines (RANTES and MCP-1) thereby delaying the onset of and severity of autoimmune symptoms in MRL/lpr mouse model.

Purification and identification of chemokines potentially involved in kidney-specific metastasis by a murine lymphoma variant: induction of migration and NFkappaB activation

The ESb-MP cell line is the subclone of a highly malignant variant of murine methylcholanthrene-induced T lymphoma, ESb. When injected in vivo, ESb-MP cells metastasize to the kidney with high frequency, whereas a non-adherent variant, ESb cells, rarely form metastatic foci in the kidney. Our previous results showed that ESb-MP, but not ESb, cells were able to migrate in response to murine kidney-conditioned media (KCM). In an effort to characterize the tumor cell chemoattractant(s) produced by kidney cells, we found that the murine kidney mesangial cell line MES-13 released more chemotactic activity for ESb-MP cells than present in KCM. A major heparin-binding chemotactic activity was purified to homogeneity by sequential fast-performance liquid chromatography and reversed phase high-performance liquid chromatography. Amino acid sequencing of the formic acid-digested active fractions revealed that the purified protein was identical to murine MCP-1(JE) and its activity was neutralized by an anti-MCP-1(JE) antibody. Another chemokine, RANTES, was also purified from MES-13 cell supernatant. The chemotactic activity contained in the MES-13 cell supernatant and in murine KCM was neutralized in part by a combination of anti-MCP-1(JE) and anti-RANTES antibodies. We further examined the differences in the ESb-MP and ESb cells. Binding studies using a variety of radio-iodinated chemokines showed that although both ESb-MP and ESb cells expressed substantial levels of high-affinity binding sites for CC chemokines, only ESb-MP cells migrated in response to CC chemokines and these cells constitutively expressed higher levels of beta2 integrin adhesion protein CD11b than their parental ESb cells. CC chemokines also activated NFkappaB in ESb-MP but not in ESb cells. Our results indicate that CC chemokines selectively chemoattract and activate ESb-MP cells. Thus, locally produced chemokines, MCP-1(JE) and RANTES in particular, may contribute to the preferential metastasis of ESb-MP cells to the kidneys.

Production and characterization of recombinant active mouse gelatinase B from eukaryotic cells and in vivo effects after intravenous administration

Gelatinase B is a matrix metalloproteinase involved in tissue remodelling. When mouse cells are triggered in vitro with interleukin-1, bacterial endotoxin, virus-mimicking double-stranded RNA or cytokine inducers, they produce gelatinase B. To test the effects of gelatinase B in vivo, the enzyme was expressed in Chinese hamster ovary (CHO) cells. Hybrid genomic DNA-cDNA constructs under the control of two constitutive viral promoters were generated by PCR-mediated exon amplification. In vitro transcription and translation of the mRNA in reticulocyte lysate yielded the correct 79-kDa protein, and expression in CHO cells resulted in an intact glycosylated 110-kDa gelatinase B which was enzymically active. However, the production yields of recombinant enzyme from 50 tested clones were low and cell-culture supernatants contained significant amounts of copurifiable endogenous CHO gelatinase B. Therefore, the enzyme was expressed in the yeast Pichia pastoris. Recombinant proenzyme was secreted and recovered from the yeast culture medium at 10 mg/l. Amino-terminal sequence analysis indicated that affinity purification of the recombinant protein on gelatin-Sepharose yielded the expected N-glycosylated proenzyme form (110 kDa) in addition to an amino-terminally truncated unglycosylated variant (69 kDa). Both forms had gelatinolytic activity on zymography. The recombinant mouse gelatinase B was used to determine its pharmacokinetics and its haematological effects in vivo. After intravenous injection in rabbits, gelatinase B disappeared from the circulation within 6 h. In addition to a transient leukopenia, we observed a rapid increase in leukocytosis, which indicates that gelatinase B might be a factor involved in the desorption of adherent leukocytes from the vascular bed and in the release of leukocytes from the bone marrow. Gelatinase B secretion and activation might well be one of the crucial molecular mechanisms explaining leukocytosis which is associated with infections and almost all types of inflammation.

Leukocyte migration and activation by murine chemokines

Chemokines are a family of chemotactic cytokines which attract different types of leukocytes. This property, combined with some additional inflammatory and growth-regulatory activities, demonstrate their crucial role in the immune system. Chemokines are low molecular weight proteins and possess a typical positioning of four conserved cysteines. This family is further subdivided in two subfamilies depending on whether the first two cysteines are adjacent or not (CC and CXC chemokines, respectively). The CXC chemokines (including interleukin-8) predominantly attract neutrophils, whereas CC chemokines induce migration of monocytes, as well as other leukocyte cell types. In this article, the general characteristics of chemokines are reviewed. Furthermore, the murine CC chemokines, JE/MCP-1, MCP-3/MARC, MIP-1 alpha, MIP-1 beta, RANTES, TCA3, C10/MRP-1, MRP-2, and eotaxin, are discussed more in detail.

Chemokines: a superfamily of chemotactic cytokines

Chemokines are a bipartite family of chemotactic proteins that bear the structural hallmark of four cysteine residues, the first two of which are in tandem. The spectrum of action of chemokines encompasses a large number of leukocyte populations, including monocytes, granulocytes, lymphocytes, NK and dendritic cells. Although the spectrum of action of chemokines largely overlaps, clear differences are still present. Chemokines play an important role in the recruitment of leukocytes at the site of inflammation, allergic reaction and tumors. Available information on receptor usage by MCP-1 and related chemokines and signal transduction pathways is reviewed. The better understanding of signaling mechanisms will provide a new basis for the development of therapeutic strategies.

Suppression of tumor growth and metastasis of murine renal adenocarcinoma by syngeneic fibroblasts genetically engineered to secrete the JE/MCP-1 cytokine

The murine monocyte chemoattractant protein 1, JE/MCP-1, like its human counterpart monocyte chemotactic and activating factor (MCAF), attracts monocytes-macrophages to tumor tissues. In previous studies we reported that expression of the JE/MCP-1 gene in murine colon carcinoma cells reduced their tumorigenicity and suppressed their metastatic potential. We now demonstrate that the growth and metastasis of the renal adenocarcinoma cell line RENCA are reduced when it was admixed with syngeneic fibroblasts engineered to secrete the JE/MCP-1 cytokine before injection. Culture supernatants of JE/MCP-1-expressing cells plus lipopolysaccharide (LPS) synergistically activated tumoricidal properties in syngeneic macrophages against RENCA cells. This activity was blocked by anti-JE/MCP-1 antibody, indicating that JE/MCP-1 was involved in priming the macrophages to respond to LPS. Moreover, alveolar macrophages isolated shortly after iv injections of JE/MCP-1 transfected cells were cytotoxic to RENCA cells in vitro. Collectively, these data suggest that in addition to its chemotactic properties, JE/MCP-1 can synergize with bacterial endotoxins to activate macrophages, thus providing a rationale for the use of the JE/MCP-1 protein as a modality for treatment of metastasis.

Identification of MIP-1 alpha/LD78 as a monocyte chemoattractant released by the HTLV-I-transformed cell line MT4

It is known that the HTLV-I-transformed cell line MT4 releases chemotactic activity for monocytes spontaneously. The MT4 monocyte chemoattractant was purified to homogeneity and sequencing of 25 amino acids revealed identity with the C-C chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha/LD78). An anti-MIP-1 alpha/LD78 rabbit antiserum substantially inhibited chemotaxis of the MT4 chemoattractant. MT4 cells constitutively expressed MIP-1 alpha/LD78 but not the C-C chemokines MCP-1, RANTES, and MIP-1 beta/Act2 and the C-X-C chemokines IL-8, gro alpha, and gro beta. MT4-derived MIP-1 alpha/LD78 was active on monocytes but was a weak chemoattractant for polymorphonuclear leukocytes. Thus, MIP-1 alpha/LD78 is a major monocyte chemoattractant released by HTLV-I-transformed T cells. Expression of MIP-1 alpha/LD78, a leukocyte chemotactic and myelosuppressive molecule, may play an important role in the manifestations of HTLV-I-related diseases.

Expression of the JE/MCP-1 gene suppresses metastatic potential in murine colon carcinoma cells

The purpose of this study was to determine whether the expression of the JE/MCP-1 gene encoding for the monocyte chemottractant protein, MCP-1 (also known as monocyte chemotactic and activating factor MCAF, TDCF, and SMC-CF) can influence the metastatic properties of tumor cells. The highly metastatic murine colon carcinoma CT-26 cells, syngeneic to BALB/c mice that do not produce endogenous JE/MCP-1 protein, were transfected with a BCMGS-Neo expression vector (control) or a vector containing full-length JE cDNA. CT-26 parental cells, CT-26 Neo, and CT-26 JE/MCP-1-positive cells were injected into syngeneic or nude mice. The CT-26 JE/MCP-1-positive cells produced significantly fewer lung metastases. The decrease in incidence of metastasis was not due to the inability of the transfected cells to arrest in the lung vasculature or to differences in cell cycle time. CT-26 cells producing JE/MCP-1 were highly susceptible to lysis by syngeneic macrophages treated with subthreshold concentrations of lipopolysaccharide. In addition, culture supernatants of JE/MCP-1-expressing cells plus lipopolysaccharide synergistically activated tumoricidal properties in syngeneic macrophages. This activity was blocked by anti-JE/MCP-1 antibodies, indicating the involvement of the JE/MCP-1 molecule in this process. Moreover, purified JE/MCP-1 added to lipopolysaccharide-containing medium resulted in significant activation of macrophages against parental CT-26 cells. These data suggest that, in addition to its chemotactic properties, JE/MCP-1 can synergize with bacterial endotoxins to activate macrophages to become tumoricidal and, hence, could suppress metastasis.

Glycoforms modify the dynamic stability and functional activity of an enzyme

Glycoproteins generally consist of collections of glycosylated variants (glycoforms) in which an ensemble of different oligosaccharides is associated with each glycosylation site. Bovine pancreatic ribonuclease B occurs naturally as a mixture of five glycoforms in which the same polypeptide sequence is associated with a series of oligomannose sugars attached at the single N-glycosylation site. Individual glycoforms were prepared by exoglycosidase digestions of RNase B and analyzed directly at the protein level by capillary electrophoresis. For the first time, electrophoretically pure single glycoforms have been available to explore the possibility that different sugars might specifically modify the structure, dynamics, stability, and functional properties of the protein to which they are attached. Comparisons of the amide proton exchange rates for individual glycoforms of RNase B and unglycosylated RNase A showed that while the 3D structure was unaffected, glycosylation decreased dynamic fluctuations throughout the molecule. There was individual variation in the NH-ND exchange rates of the same protons in different glycoforms, demonstrating the effects of variable glycosylation on dynamic stability. Consistent with the overall decrease in flexibility, and with the possibility that all of the sugars may afford steric protection to susceptible sites, was the finding that each of the glycoforms tested showed increased resistance to Pronase compared with the unglycosylated protein. In a novel sensitive assay using double-stranded RNA substrate, the different glycoforms showed nearly a 4-fold variation in functional activity; molecular modeling suggested that steric factors may also play a role in modulating this interaction.

Species-specificity of monocyte chemotactic protein-1 and -3

The present study was aimed at defining the activity of human and mouse monocyte chemotactic protein-1 (MCP-1) on homologous and heterologous mononuclear phagocytes. Human natural and recombinant MCP-1 and mouse natural MCP-1/JE were tested as chemoattractants on human blood monocytes and mouse peritoneal macrophages. The human and murine cytokines were equiactive on human monocytes. Human MCP-1 was active on mouse macrophages but the maximal chemotactic effect elicited was about half that of human cells or of mouse MCP-1/JE or of reference chemoattractants. Human MCP-3, a recently identified member of the C-C chemokine family, with high sequence similarity to MCP-1/JE, was also active on mouse mononuclear phagocytes, though less so than mouse MCP-1/JE. These results caution against under-estimating the potential of MCPs when the human chemokines are applied in mice.

Mouse gelatinase B. cDNA cloning, regulation of expression and glycosylation in WEHI-3 macrophages and gene organisation

Gelatinase B is a regulated matrix metalloproteinase with an important role in the remodelling of extracellular matrices and of basement membranes. To study the structure and function of gelatinase B in the mouse, the cDNA was cloned from a macrophage cell line (WEHI-3). Using this cDNA, a cosmid clone with the mouse gene was isolated. The complete gene (8 kbp) was sequenced and compared with the human gene structure. There was 78% similarity at the cDNA level and the exon/intron structure of the murine gene was similar to the human counterpart. At the 5' untranslated side, 1200 bp of the promoter/enhancer region were sequenced and found to contain several transacting-factor-binding sites. The mRNA transcription-initiation site was determined by non-isotopic primer-extension analysis. Polymerase-chain-reaction amplification of cDNAs yielded indirect evidence for a reverse-transcription stop in WEHI-3 cell mRNA. The DNA-derived mouse-protein structure exhibited 82% similarity with the human one. This similarity was functionally reflected by cross-reactivity of the mouse protein with an antiserum against human gelatinase B. The production of murine gelatinase B was studied at the protein level by zymography and at the mRNA level by Northern blot analysis. In WEHI-3 cells the gelatinase B protein is induced by bacterial lipopolysaccharide, phorbol ester, double-stranded RNA and the cytokine interleukin-1. Regulation of activity and structural heterogeneity of gelatinase B in WEHI-3 cells were shown to occur at the gene regulatory level, by expression of the matrix metalloproteinase inhibitor TIMP-1, and by glycosylation of the secreted protein.