Cloning and sequencing of the cDNA for human monocyte chemotactic and activating factor (MCAF)

Human MCAF gene transfer enhances the metastatic capacity of a mouse cachectic adenocarcinoma cell line in vivo

PURPOSE

To evaluate the effect of monocyte chemotactic and activating factor (MCAF/MCP-1/JE) on tumor progression and metastasis.

METHODS

Cachexia-inducing adenocarcinoma cells (cell line colon 26, clone 20) were transfected with either a control plasmid or MCAF expression vector. Spontaneous lung metastases were determined in mouse.

RESULTS

The production of MCAF reached 0.4 ng/ml in vitro when transfectant cells were cultured at a cell density of 5 x 10(4) cells/ml for 3 days. Transfection of MCAF expression vector did not affect the growth rate in vitro. Also, after MCAF-transfection, the size of tumors after intra-footpad inoculation was similar to that of the parental cells. When the primary tumors were resected on the 10th day after inoculation, the incidence of spontaneous lung metastasis was less than 20% in both cells. The number of endothelial cells in the primary tumor rapidly increased from the 10th to the 14th day after inoculation, as revealed by immunohistochemical staining. In accordance with enhanced angiogenesis, the incidence rates of spontaneous metastasis increased when the primary tumors were resected on the 14th day after inoculation. Moreover, the spontaneous lung metastases were augmented in the animals injected with MCAF-transfectants compared to those injected with parental cells with a concomitant increase of angiogenesis.

CONCLUSIONS

These results suggest that MCAF may augment the metastastic potential by modulating tumor associated angiogenesis.

Production and cytokine-mediated regulation of monocyte chemoattractant protein-1 by human proximal tubular epithelial cells

Impairment of renal function in various types of glomerular disease is associated with tubulointerstitial changes. The mechanism of mononuclear cell infiltration in the interstitium is not fully understood. Recently, monocyte chemoattractant protein-1 (MCP-1) has been identified as a monocyte-specific chemotactic factor. We analyzed the presence of MCP-1 in renal biopsies from patients with various forms of glomerular disease and demonstrated that MCP-1 expression is increased in renal tubular epithelial cells during disease. Further analysis showed that various cell lines of human proximal tubular epithelial cells (PTEC) produce MCP-1 in culture under serum-free conditions and that the production is inhibited by cycloheximide. IL-1 alpha and TNF-alpha enhanced the production by each cell line in a dose- and time-dependent manner as measured by radioimmunoassay. Northern blot analysis demonstrated that IL-1 alpha and TNF-alpha markedly enhanced the expression of MCP-1 mRNA. Taken together these observations support the notion that MCP-1 is synthesized de novo by PTEC. MCP-1 produced by PTEC is found to be 13 kD by gel filtration chromatography. It is chemotactically active for monocytes. We conclude that in various types of glomerular disease, MCP-1 expression in tubular epithelial cells is associated with up-regulation of MCP-1 production by PTEC. These findings raise the possibility that macrophages may accumulate in renal interstitium as a consequence of MCP-1 production by PTEC.

Chemokine gene transfection into tumour cells reduced tumorigenicity in nude mice in association with neutrophilic infiltration

To study the effect of localised secretion of chemokines on tumour growth, the genes for human (hu) interleukin 8 (IL-8), hu-MCP-1 (MCAF), hu-MIP-1 alpha (LD78), murine (mu)-MCP-1 (JE), mu-MIP-1 alpha or mu-MIP-2 were introduced, via mammalian expression vectors, into Chinese hamster ovary (CHO) cells, and the ability of transfected cells to form tumours in vivo was evaluated. The production of hu-IL-8, hu-MIP-1 alpha or mu-MIP-1 alpha by transfected clones did not influence the growth rate in vitro, but drastically suppressed tumour growth when injected subcutaneously (s.c.) into nude mice. However, clones transfected with hu-MCP-1, mu-MCP-1 or mu-MIP-2 did not show any significant difference in growth rate in vivo compared with clones transfected with vector alone. Histological examination of the site of injection of CHO clones transfected with hu-IL-8, hu-MIP-1 alpha or mu-MIP-1 alpha showed predominantly neutrophilic infiltration. These results indicate that chemokines have potent anti-tumour activity when released, even at low doses, at the tumour site, which may be mediated by recruitment and targeting of neutrophilic granulocytes to chemokine-releasing cells. Our studies highlight the potential usefulness of localised chemokine secretion in inducing potent host anti-tumour defensive responses.

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.

Induction of monocyte chemoattractant protein-1 synthesis in human monocytes during transendothelial migration in vitro

Monocyte chemoattractant protein-1 (MCP-1, or monocyte chemotactic and activating factor) plays important roles in the recruitment of monocytes and thus in the development of atherosclerosis. In this study, we determined whether MCP-1 synthesis was induced by the cellular interaction between monocytes and endothelial cells during the process of transendothelial migration. We found that when human peripheral blood monocytes (2.5 x 10(6) cells) and umbilical vein endothelial cells (HUVECs; 5.0 x 10(5) cells) were cocultured for 5 hours, 7.9 ng/mL MCP-1 was secreted into the medium, whereas when the two were cultured separately, MCP-1 levels were 1.0 and 0.9 ng/mL, respectively. Furthermore, the use of interleukin-1 beta (IL-1 beta)-pretreated HUVECs in cocultures induced twice the levels of MCP-1 as in unstimulated HUVEC culture. Conditioned medium had transendothelial chemotactic activity for monocytes, and this activity was completely abolished by addition of anti-MCP-1 antibody. Although MCP-1 mRNA levels were very low or undetectable in HUVECs or monocytes alone, message could be detected after 2 hours of coculture in total mRNA preparations from both monocytes and HUVECs. mRNA levels increased by 4 hours and had declined slightly by 24 hours. The rapid induction of message suggests that cell contact between monocytes and HUVECs induces the de novo synthesis of MCP-1 protein. Anti-interleukin (IL)-1 alpha/beta and anti-tumor necrosis factor-alpha antibodies, or anti-lymphocyte function-associated antigen-1 and very late antigen-4 antibodies, had little or no inhibitory effects on MCP-1 secretion by cocultures.(ABSTRACT TRUNCATED AT 250 WORDS)

The detection and localization of monocyte chemoattractant protein-1 (MCP-1) in human ovarian cancer

Chemokines may control the macrophage infiltrate found in many solid tumors. In human ovarian cancer, in situ hybridization detected mRNA for the macrophage chemokine monocyte chemoattractant protein-1 (MCP-1) in 16/17 serous carcinomas, 4/4 mucinous carcinomas, 2/2 endometrioid carcinomas, and 1/3 borderline tumors. In serous tumors, mRNA expression mainly localized to the epithelial areas, as did immunoreactive MCP-1 protein. In the other tumors, both stromal and epithelial expression were seen. All tumors contained variable numbers of cells positive for the macrophage marker CD68. MCP-1 mRNA was also detected in the stroma of 5/5 normal ovaries. RT-PCR demonstrated mRNA for MCP-1 in 7/7 serous carcinomas and 6/6 ovarian cancer cell lines. MCP-1 protein was detected by ELISA in ascites from patients with ovarian cancer (mean 4.28 ng/ml) and was produced primarily by the cancer cells. Human MCP-1 protein was also detected in culture supernatants from cell lines and in ascites from human ovarian tumor xenografts which induce a peritoneal monocytosis in nude mice. We conclude that the macrophage chemoattractant MCP-1 is produced by epithelial ovarian cancer and that the tumor cells themselves are probably a major source. MCP-1 may contribute to the accumulation of tumor-associated macrophages, which may subsequently influence tumor behavior.

Chemokines, a family of chemotactic cytokines

Chemokines are low-molecular-weight proteins that stimulate recruitment of leukocytes. They are secondary pro-inflammatory mediators that are induced by primary pro-inflammatory mediators such as interleukin-1 (IL-1) or tumor necrosis factor (TNF). The physiologic importance of this family of mediators is derived from their specificity. Unlike the classic leukocyte chemo-attractants, which have little specificity, members of the chemokine family induce recruitment of well-defined leukocyte subsets. Thus, chemokine expression can account for the presence of different types of leukocytes observed in various normal or pathologic states. There are two major chemokine sub-families based upon the position of cysteine residues, i.e., CXC and CC. All members of the CXC chemokine sub-family have an intervening amino acid between the first two cysteines; members of the CC chemokine sub-family have two adjacent cysteines. As a general rule (with some notable exceptions), members of the CXC chemokines are chemotactic for neutrophils, and CC chemokines are chemotactic for monocytes and a small sub-set of lymphocytes. This review discusses the potential role of chemokines in inflammation and focuses on the two best-characterized chemokines, monocyte chemoattractant protein-1 (MCP-1), a CC chemokine, and interleukin-8 (IL-8), a member of the CXC chemokine sub-family.

Signal transduction and ligand specificity of the human monocyte chemoattractant protein-1 receptor in transfected embryonic kidney cells

We have examined the ligand specificity and signal transduction pathways of a recently cloned receptor for monocyte chemoattractant protein-1 (MCP-1). In human 293 cells stably transfected with the MCP-1 receptor, MCP-1 bound specifically with high affinity (Kd = 260 pM) and induced a rapid mobilization of calcium from intracellular stores. The closely related chemokines MIP-1 alpha, MIP-1 beta, RANTES, interleukin 8 (IL-8), and Gro-alpha were inactive at concentrations as high as 300 nM. Activation of the MCP-1 receptor potently inhibited adenylyl cyclase with an IC50 = 90 pM. Activation of the MIP-1 alpha/RANTES receptor also mediated inhibition of adenylyl cyclase activity but with a different pharmacological profile: MIP-1 alpha (110 pM, IC50), RANTES (140 pM), MIP-1 beta (10 nM), and MCP-1 (820 nM). Mobilization of intracellular calcium and inhibition of adenylyl cyclase were blocked by pertussis toxin, suggesting that the MCP-1 receptor coupled to G alpha i. These results demonstrate that the MCP-1 receptor binds and signals in response to picomolar concentrations of MCP-1 in a highly specific manner. Signaling was manifested as mobilization of intracellular calcium and inhibition of adenylyl cyclase and was mediated by a pertussis toxin-sensitive G-protein(s).

Heterogeneity of cytokine and growth factor gene expression in human melanoma cells with different metastatic potentials

The purpose of this study was to determine the mRNA expression level of multiple cytokine and growth factor genes in human malignant melanoma. Melanoma cells were isolated from several surgical specimens, adapted to growth in culture, characterized for their ability to produce experimental metastases in nude mice, and assessed for cytokine and growth factor steady-state gene expression. Highly metastatic in vivo- and in vitro-derived variants isolated from a single melanoma, A375, were also analyzed. Northern blot analyses revealed that all melanomas analyzed constitutively expressed steady-state mRNA transcripts for the growth and angiogenic factors, basic fibroblast growth factor (bFGF), and transforming growth factor alpha (TGF-alpha), which correlated with metastatic propensity. Only one highly metastatic melanoma, TXM-1, originally isolated from a lymph node metastasis, expressed mRNA transcripts specific for monocyte chemotactic and activating factor (MCAF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Similarly, of the nine melanomas examined, only TXM-1 expressed interleukin (IL)-1 alpha, IL-1 beta, and IL-6, important immunomodulatory cytokines. These data demonstrate the differential and heterogeneous expression of cytokine and growth factor genes in human malignant melanoma.

Monocyte chemotactic protein-1 (MCP-1) mRNA is down-regulated in human dermal fibroblasts by dexamethasone: differential regulation by TGF-beta

Macrophages are a source of cytokines driving repair. Wound macrophages are derived from circulating monocytes. Monocyte chemotactic protein-1 (MCP-1) is a potent specific monocyte chemoattractant. Treatment of serum stimulated dermal fibroblasts with dexamethasone led to a dose dependent down-regulation of MCP-1 mRNA levels. Such an anti-inflammatory effect may partially explain the negative influence of glucocorticoid treatment on wound repair. Topical or parenteral of fibroblasts cultured in serum free media with TGF-beta increased MCP-1 mRNA levels. TGF-beta treatment of fibroblasts cultured in serum also partially overcame the dexamethasone mediated decrease in MCP-1 mRNA levels. In glucocorticoid treated animals TGF-beta may stimulate repair by an indirect pro-inflammatory action following transcriptional up-regulation of MCP-1.

Monocyte-chemoattractant protein 1 gene expression in intestinal epithelial cells and inflammatory bowel disease mucosa

BACKGROUND

Monocyte-chemoattractant protein 1 (MCP-1) activates macrophages and increases the migration of monocytes into tissue during inflammation. It was hypothesized that MCP-1 expression is involved in intestinal inflammation.

METHODS

MCP-1 protein was detected by immunohistochemistry and immunoprecipitation. Biological activity of MCP-1 was assessed using a chemotactic assay. MCP-1 messenger RNA (mRNA) levels were measured by quantitative reverse-transcription polymerase chain reaction.

RESULTS

In normal mucosa, MCP-1 was predominantly present in surface epithelium. In contrast, inflamed mucosa from patients with ulcerative colitis or Crohn's disease contained multiple cells immunoreactive for MCP-1, including spindle cells, mononuclear cells, and endothelial cells. Furthermore, MCP-1 mRNA expression was markedly increased in inflamed intestinal biopsy specimens from patients with inflammatory bowel disease. MCP-1 was detected in isolated intestinal epithelial cells and in conditioned media from Caco-2 cells. Caco-2 cell-conditioned media stimulated monocyte chemotaxis activity that was inhibited by anti-MCP-1 antibodies. Constituitive MCP-1 mRNA levels in Caco-2 cells were up-regulated by interleukin 1 beta and down-regulated by dexamethasone.

CONCLUSIONS

In addition to lamina propria macrophages, endothelial cells, and spindle cells, intestinal epithelial cells are able to produce MCP-1. MCP-1 is expressed constitutively in the intestinal colonic mucosa and is up-regulated during inflammation.

Effect of cytokines on mediator release from human dispersed lung mast cells

To evaluate the contribution of human lung mast cells (HLMC) to allergic inflammation, we investigated whether or not cytokines, including stem-cell factor (SCF), monocyte chemotactic and activating factor (MCAF), and RANTES, activate HLMC. SCF induced histamine release from dispersed HLMC in a dose-dependent fashion (P < 0.01). The release was 7.8 +/- 1.0% at 500 ng/ml SCF (n = 9). This response was also observed in chopped lung tissue. HLMC from which surface IgE molecules had been removed by treatment with lactic acid responded to SCF, while these cells lost their response to anti-IgE. The process was relatively rapid and reached a maximum in 5 min. This response required extracellular calcium, and it was observed at 37 degrees C, but not at 4 degrees C or 20 degrees. A brief preincubation (10 min) with lower concentrations of SCF, which were ineffective in releasing histamine, enhanced anti-IgE-induced histamine release (P < 0.05), while its enhancing effect was lost by the longer preincubation (30 min). SCF did not prime basophils to enhance stimulated-histamine release. Interleukin (IL)-1 alpha, IL-1 beta, IL-3, IL-4, IL-5, granulocyte/macrophage-colony stimulating factor (GM-CSF), MCAF, and RANTES neither induced histamine release nor enhanced the release stimulated by anti-IgE after a 10- or 30-min preincubation. The combination of IL-3 and IL-4 showed no effect on histamine release from HLMC. Leukotriene (LT)C4/D4/E4 production by SCF was negligible, as compared with anti-IgE-induced LT production.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

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.

Expression of the chemokine superfamily in rheumatoid arthritis

The infiltration of leucocytes into the joint of rheumatoid arthritis (RA) is believed to be mediated by chemotactic factors released by activated cells. In this study, examination was made of the gene expression and production of the chemokine superfamily in RA patients by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoprecipitation. Cultured synovial fibroblasts were found capable of expressing and producing IL-8, GRO, monocyte chemotactic and activating factor (MCAF), macrophage inflammatory protein-1 alpha (MIP-1 alpha), MIP-1 beta and RANTES in response to IL-1 alpha. The expression of IL-8, GRO, MCAF, MIP-1 alpha, and MIP-1 beta was clearly shown to increase in freshly isolated synovial fluid mononuclear cells (SFMC) of RA patients, in contrast to peripheral blood mononuclear cells (PBMC) of RA patients and normal subjects. The gene expression of RANTES appeared to be the same for RA SFMC, RA PBMC, and normal PBMC. Thus, the over-expression of various chemokines may promote the recruitment of inflammatory cells into rheumatoid inflamed joints.

Monocyte chemoattractant protein 1 acts as a T-lymphocyte chemoattractant

We have utilized a transendothelial lymphocyte chemotaxis assay to identify and purify a lymphocyte chemoattractant in supernatants of mitogen-stimulated peripheral blood mononuclear cells. Amino acid sequence analysis revealed identity with monocyte chemoattractant protein 1 (MCP-1), a chemoattractant previously thought to be specific for monocytes. Recombinant MCP-1 is chemoattractive for purified T lymphocytes and for CD3+ lymphocytes in peripheral blood lymphocyte preparations. The T-cell response to MCP-1 is dose-dependent and chemotactic, rather than chemokinetic. Phenotyping of chemoattracted T lymphocytes shows they are an activated memory subset. The response to MCP-1 by T lymphocytes can be duplicated in the absence of an endothelial monolayer and the majority of T-lymphocyte chemotactic activity in mitogen-stimulated peripheral blood mononuclear cell supernatants can be neutralized by antibody to MCP-1. Thus, MCP-1 is the major lymphocyte chemoattractant secreted by mitogen-stimulated peripheral blood mononuclear cells and is capable of acting as a potent T-lymphocyte, as well as monocyte, chemoattractant. This may help explain why monocytes and T lymphocytes of the memory subset are always found together at sites of antigen-induced inflammation.

Molecular cloning and functional expression of two monocyte chemoattractant protein 1 receptors reveals alternative splicing of the carboxyl-terminal tails

Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokine family of cytokines that mediate leukocyte chemotaxis. The potent and specific activation of monocytes by MCP-1 may mediate the monocytic infiltration of tissues in atherosclerosis and other inflammatory diseases. We have isolated cDNAs that encode two MCP-1-specific receptors with alternatively spliced carboxyl tails. Expression of the receptors in Xenopus oocytes conferred robust mobilization of intracellular calcium in response to nanomolar concentrations of MCP-1 but not to related chemokines. The MCP-1 receptors are most closely related to the receptor for the chemokines macrophage inflammatory protein 1 alpha and RANTES (regulated on activation, normal T expressed and secreted). The identification of the MCP-1 receptor and cloning of two distinct isoforms provide powerful tools for understanding the specificity and signaling mechanisms of this important chemokine.

Eotaxin: a potent eosinophil chemoattractant cytokine detected in a guinea pig model of allergic airways inflammation

Eosinophil accumulation is a prominent feature of allergic inflammatory reactions, such as those occurring in the lung of the allergic asthmatic, but the endogenous chemoattractants involved have not been identified. We have investigated this in an established model of allergic inflammation, using in vivo systems both to generate and assay relevant activity. Bronchoalveolar lavage (BAL) fluid was taken from sensitized guinea pigs at intervals after aerosol challenge with ovalbumin. BAL fluid was injected intradermally in unsensitized assay guinea pigs and the accumulation of intravenously injected 111In-eosinophils was measured. Activity was detected at 30 min after allergen challenge, peaking from 3 to 6 h and declining to low levels by 24 h. 3-h BAL fluid was purified using high performance liquid chromatography techniques in conjunction with the skin assay. Microsequencing revealed a novel protein from the C-C branch of the platelet factor 4 superfamily of chemotactic cytokines. The protein, "eotaxin," exhibits homology of 53% with human MCP-1, 44% with guinea pig MCP-1, 31% with human MIP-1 alpha, and 26% with human RANTES. Laser desorption time of flight mass analysis gave four different signals (8.15, 8.38, 8.81, and 9.03 kD), probably reflecting differential O-glycosylation. Eotaxin was highly potent, inducing substantial 111In-eosinophil accumulation at a 1-2 pmol dose in the skin, but did not induce significant 111In-neutrophil accumulation. Eotaxin was a potent stimulator of both guinea pig and human eosinophils in vitro. Human recombinant RANTES, MIP-1 alpha, and MCP-1 were all inactive in inducing 111In-eosinophil accumulation in guinea pig skin; however, evidence was obtained that eotaxin shares a binding site with RANTES on guinea pig eosinophils. This is the first description of a potent eosinophil chemoattractant cytokine generated in vivo and suggests the possibility that similar molecules may be important in the human asthmatic lung.

Protection against lethal bacterial infection in mice by monocyte-chemotactic and -activating factor

Chemotactic factors regulate the recruitment of neutrophils, lymphocytes, or monocytes-macrophages to infectious and inflammatory sites. The purpose of this study was to determine whether monocyte-chemotactic and -activating factor (MCAF [MCP-1], a JE gene product) also influences the host defense mechanism against microbial infection. We evaluated the effect of recombinant human MCAF on the survival rate of mice systemically infected with Pseudomonas aeruginosa or Salmonella typhimurium. The administration of 2.5 micrograms of MCAF 6 h before infection completely protected the mice from lethal infection. Mice with cyclophosphamide-induced leukopenia exhibiting increased susceptibility to P. aeruginosa were also endowed with resistance by the same dose of MCAF. Administration of MCAF at -6 h was critical, since MCAF given either earlier or later than -6 h failed to rescue mice from lethal infection. The in vivo effect on the survival of mice paralleled the reduced recovery of viable P. aeruginosa or S. typhimurium from the peritoneal cavity, i.e., the number of recovered bacteria from the MCAF (2.5 micrograms per mouse)-treated mice was reduced to less than 2% of control mice for P. aeruginosa and 4% of control mice for S. typhimurium at 24 h. Since MCAF exhibited chemotaxis on murine macrophages as well as enhanced phagocytosis and killing of bacteria in vitro, the activation of macrophages, followed by the recruitment into the peritoneal cavity, is responsible for eliminating bacteria and thus enhancing the survival rate.

Regulation of monocyte chemoattractant protein-1 expression in adult human non-neoplastic astrocytes is sensitive to tumor necrosis factor (TNF) or antibody to the 55-kDa TNF receptor

Infiltration of the central nervous system (CNS) by monocytes is a characteristic of many non-malignant disease processes, although the signals regulating such traffic are unclear. Tumor necrosis factor (TNF) and other inflammatory cytokines have been shown to elicit production of monocyte chemoattractant activity in glioma cells, but the regulation of such activity in non-neoplastic adult astrocytes has not been examined. We previously observed that TNF constituted a proliferative signal for non-neoplastic adult human astrocytes in vitro involving the 55-kDa TNF receptor. In the present study, we demonstrate that TNF exposure enhances the expression of monocyte chemoattractant protein-1 (MCP-1) mRNA and functional monocyte chemoattractant activity in non-neoplastic astrocytes. Results indicated that MCP-1 mRNA expression was maximal within 3 h, and was further augmented by the protein synthesis inhibitor cycloheximide (CY). Antibody (htr-9) directed against the 55-kDa TNF receptor also elicited MCP-1 mRNA expression while antibody to the 75-kDa TNF receptor (utr-1) was ineffective. Secretion of monocyte chemoattractant activity was significantly greater in TNF- or htr-9-treated astrocytes than in utr-1-treated or untreated controls; activity was abolished by treatment with antibody to MCP-1. These findings suggest that non-neoplastic adult human astrocytes may contribute to CNS inflammatory responses by mediating recruitment of peripheral blood monocytes.

Detection of monocyte chemotactic and activating factor (MCAF) in normal blood and urine using a sensitive ELISA

We developed a highly sensitive enzyme-linked immunosorbent assay (ELISA) for human monocyte chemotactic and activating factor (MCAF), an inflammatory cytokine that plays an important role in the recruitment of blood monocytes to areas of inflammation. The ELISA, which is based on a sandwich method using two newly-developed monoclonal antibodies, could quantitatively detect MCAF in the range between 2.5 pg/ml (50 fg/sample) to 300 pg/ml after incubation for a total of 2 h, and showed no cross-reactivity with various structurally-related IL-8 superfamily proteins. It was not affected by blood or urine components non-specifically, and thus was directly applicable to clinical specimens. When serum and urine samples from healthy subjects were measured, they all turned out to contain detectable levels of MCAF (more than 30 pg/ml). By gel-filtration column chromatography analysis, MCAF in the body fluids was eluted as a single peak at the position corresponding to the molecular weight of 10 kD, suggesting that it exists as a monomer form, free from carrier proteins. The established ELISA here is expected to be effectively used for the further investigations on the relationship of MCAF with various inflammatory diseases.

Liposome-encapsulated muramyl tripeptide up-regulates monocyte chemotactic and activating factor gene expression in human monocytes at the transcriptional and post-transcriptional levels

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a novel immune modulator that is now under investigation against metastatic melanoma and osteosarcoma. We have already reported that L-MTP-PE induced monocyte-mediated tumoricidal activity and up-regulation of the tumor necrosis factor and interleukin-1 (IL-1) in vivo and in vitro. We now demonstrate that L-MTP-PE also induces monocyte chemotactic and activating factor (MCAF) mRNA expression at both the transcriptional and post-transcriptional levels. Monocyte chemotactic activity was also present in the supernatants of L-MTP-PE-stimulated cells. In monocytes, the increased expression of MCAF was induced rapidly (by 2 h) but was short-lived. By 4 h, MCAF mRNA had decreased to background level. We found no change in MCAF mRNA levels in lymphocytes exposed to L-MTP-PE. We therefore conclude that L-MTP-PE selectively up-regulates MCAF expression in monocytes and that MCAF may play a role in the tumoricidal and immune-stimulating activity of L-MTP-PE.

Interferon-gamma Stimulates Monocyte Chemotactic Protein-1 Expression by Monocytes

Monocyte chemotactic protein (MCP-1) is a specific monocyte chemoattractant and activating factor produced by both immune cells (mononuclear phagocytes and lymphocytes) and non-immune cells (parenchymal and stromal cells). In order to define the conditions under which human monocytes express MCP-1, monocytes were exposed to IFN-γ, IL- lβ, TNF-α, IL-4 or PHA under serum free conditions. There was no significant MCP-1 production by monocytes following exposure to IL-lβ, TNF-α or IL-4. In contrast, stimulation with IFN-γ resulted in a dose dependent increase in MCP-1 protein and mRNA expression. Simultaneous stimulation with IFN-γ and IL-1β or TNF-α resulted in no further increase in MCP-1 production. It is concluded that IFN-γ, primarily a product of T_H1 T lymphocytes, stimulates the expression of MCP-1 by monocytes.

Composite origin of major histocompatibility complex genes

Major histocompatibility complex (MHC) genes have now been cloned from representatives of all vertebrate classes except Agnatha. The recent accumulation of sequence data has given great insight into the course of evolution of these genes. Although the primary structure of the MHC genes varies greatly from class to class and also within the individual classes, the general features of the tertiary and quaternary structure have been conserved remarkably well during more than 400 million years of evolution. The ancestral MHC genes may have been assembled from at least three structural elements derived from different gene families. Class II MHC genes appear to have been assembled first, and then to have given rise to class I genes.

The expression of monocyte chemotactic protein (MCP-1) in human vascular endothelium in vitro and in vivo

A monocyte chemotactic protein (MCP-1) is thought to play a major role in recruiting monocytes to the vascular endothelium where the adherence of monocytes is one of the earliest events in atherogenesis. We cloned MCP-1 cDNA from a lambda gt 11 cDNA library constructed from human aortic endothelial mRNA to test whether MCP-1 expressed in arterial endothelium is identical to those from other sources. A approximately 670 bp MCP-1 cDNA clone was identified and showed the identical sequence with the ones from other cell lines. Northern blot analysis using this cloned MCP-1 cDNA as probe revealed two hybridizing bands of RNA at 0.68 and 0.77 kb in human aortic, human pulmonary arterial, and human umbilical vein endothelial cell cultures. Primer extension analysis showed that the difference in size (approximately 90 bp) between the two transcripts is not due to a difference at the 5'-noncoding region. The amount of MCP-1 transcripts increased dramatically in aortic endothelial cells when stimulated with recombinant IL-1 alpha (100 units/ml), IL-1 beta (100 units/ml), or TNF-alpha (200 ng/ml). Northern blot and slot blot analysis of RNA isolated from both the endothelium and the underlying vessel wall of freshly removed human arteries and veins showed MCP-1 transcripts. This observation demonstrates for the first time that MCP-1 is expressed not only in atherosclerotic human arteries but also in symptom free arteries and veins in vivo.

Expression of monocyte chemotactic and activating factor (MCAF) in skin related cells. A comparative study

A significant proportion of the infiltrating cells in several inflammatory skin diseases, including psoriasis and allergic contact dermatitis, are monocytes. Additionally, it is known that the cytokine monocyte chemotactic and activating factor (MCAF) can be produced by several cell types present in the skin, suggesting a significant role for MCAF in the accumulation of monocytes during immunological and inflammatory skin reactions. We have recently developed a precise method for quantification of the amount of a specific mRNA species in a given sample and have used this technique to compare specific MCAF mRNA amounts in cultures of human keratinocytes, dermal fibroblasts, endothelial cells, and monocytes, after stimulation with interleukin 1 alpha (IL-1 alpha) for 6 h. Endothelial cells produced very high, monocytes and fibroblasts intermediate, and keratinocytes low amounts of MCAF mRNA. We have also performed time course studies of MCAF mRNA levels in the four cell types. Our findings suggest that the regulation of MCAF mRNA expression in these cells parallels the regulation of the lymphocyte and neutrophil chemotactic factor interleukin 8.

Expression of monocyte chemotactic and activating factor in rheumatoid arthritis. Regulation of its production in synovial cells by interleukin-1 and tumor necrosis factor

OBJECTIVE

To investigate whether monocyte chemotactic and activating factor (MCAF) contributes to the accumulation of macrophages in the joints of patients with rheumatoid arthritis (RA).

METHODS

MCAF was measured by radioimmunoassay. MCAF gene expression was determined by Northern blotting and reverse-transcriptase polymerase chain reaction. Recombinant human MCAF was injected into rabbit joints to evaluate the effect of MCAF on infiltration of macrophages.

RESULTS

High levels of MCAF were detected in synovial fluid from patients with RA. Cells freshly isolated from synovial fluid expressed MCAF messenger RNA (mRNA). Fibroblast-like synoviocytes were found to express MCAF mRNA and to secrete MCAF in response to interleukin-1 (IL-1) and tumor necrosis factor in vitro. IL-1 also promoted MCAF gene expression in rabbit synovial tissue in vivo. MCAF caused marked infiltration of macrophages in rabbit synovial tissue.

CONCLUSION

Our findings suggest that MCAF may contribute to the accumulation of macrophages in inflamed rheumatoid joints.

The product of a novel growth factor-activated gene, fic, is a biologically active "C-C"-type cytokine

We have characterized a new member of the superfamily of proinflammatory peptides encoded by a growth factor-inducible gene, fic, previously isolated by differential screening of a cDNA library of mRNA from serum-stimulated NIH 3T3 cells. Immunoprecipitation analyses showed that the protein was rapidly induced following serum stimulation and secreted unglycosylated into the medium. The fic protein, FIC, shows highest sequence homology (57%) to human and rabbit monocyte chemoattractant protein 1 (MCP-1), an established monocyte activator. To determine the biological activity of FIC and to compare it with that of mouse MCP-1 (muMCP-1), both proteins were expressed in the baculovirus system. FIC and muMCP-1 were purified to near homogeneity by a two-step chromatography protocol. Both proteins elicited changes in intracellular calcium concentration in human monocytes. The effect was dependent on external Ca2+ and was inhibited by pretreatment of cells with pertussis toxin. FIC did not desensitize human monocytes to the three related cytokines muMCP-1, human MCP-1 (huMCP-1), and huMCP-2. However, pretreatment with muMCP-1 or huMCP-1, but not with huMCP-2, desensitized human monocytes to FIC. Specific binding of [125I]FIC was found in human monocytes, mouse monocytic cultured cells, and human endothelial cells but not in lymphocytes, neutrophils, or primary mouse fibroblasts. Scatchard analysis of the binding of [125I]FIC to human monocytes showed the presence of two classes of receptors, with apparent KdS of 1.2 and 7.7 nM and receptor numbers per cell of 2,400 and 6,300, respectively. FIC, muMCP-1, and huMCP-1 competed to the same extent for the binding of [125I]FIC to human monocytes, contrary to huMCP-2, which competed very ineffectively, if at all.

The product of a novel growth factor-activated gene, fic, is a biologically active "C-C"-type cytokine

We have characterized a new member of the superfamily of proinflammatory peptides encoded by a growth factor-inducible gene, fic, previously isolated by differential screening of a cDNA library of mRNA from serum-stimulated NIH 3T3 cells. Immunoprecipitation analyses showed that the protein was rapidly induced following serum stimulation and secreted unglycosylated into the medium. The fic protein, FIC, shows highest sequence homology (57%) to human and rabbit monocyte chemoattractant protein 1 (MCP-1), an established monocyte activator. To determine the biological activity of FIC and to compare it with that of mouse MCP-1 (muMCP-1), both proteins were expressed in the baculovirus system. FIC and muMCP-1 were purified to near homogeneity by a two-step chromatography protocol. Both proteins elicited changes in intracellular calcium concentration in human monocytes. The effect was dependent on external Ca2+ and was inhibited by pretreatment of cells with pertussis toxin. FIC did not desensitize human monocytes to the three related cytokines muMCP-1, human MCP-1 (huMCP-1), and huMCP-2. However, pretreatment with muMCP-1 or huMCP-1, but not with huMCP-2, desensitized human monocytes to FIC. Specific binding of [125I]FIC was found in human monocytes, mouse monocytic cultured cells, and human endothelial cells but not in lymphocytes, neutrophils, or primary mouse fibroblasts. Scatchard analysis of the binding of [125I]FIC to human monocytes showed the presence of two classes of receptors, with apparent KdS of 1.2 and 7.7 nM and receptor numbers per cell of 2,400 and 6,300, respectively. FIC, muMCP-1, and huMCP-1 competed to the same extent for the binding of [125I]FIC to human monocytes, contrary to huMCP-2, which competed very ineffectively, if at all.

Cytokine-induced expression of mRNAs for chemotactic factors in human synovial cells and fibroblasts

In response to interleukin 1 or tumor necrosis factor, human synovial cells and fibroblasts expressed several genes encoding known chemotactic factors or related proteins. Transcripts for interleukin 8 (IL-8), gro/MGSA, pAT 464, IP-10, pAT 744 and Monocyte Chemotactic and Activating Factor (MCAF) accumulated rapidly in IL-1 and TNF-treated cells. The inhibition of protein synthesis led to the superinduction of IL-8 and gro/MGSA mRNAs in IL-1, but not in TNF-treated cells. Thus, IL-1 and TNF are likely to regulate the expression of these mRNAs by different mechanisms. Important cell-specific differences in mRNA accumulation characterized the expression of chemotactic factor genes. Moreover, only a subset of the same genes was activated in quiescent cells stimulated by serum. Therefore, genes encoding closely related proteins each had a distinct pattern of expression. continuous stimulation of fibroblasts and synovial cells with IL-1 resulted in high and prolonged expression of IL-8 and gro/MGSA mRNAs. These results extend the list of chemotactic factor genes expressed by mesenchymal cells in vitro and suggest a pivotal role for these cells in processes such as chronic inflammation.

Common target for 12-O-tetradecanoylphorbol-13-acetate and ras in the transcriptional enhancer of the growth factor-inducible JE gene

JE gene expression in the mouse osteoblast cell line MC3T3-E1 is activated transiently by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). In ras-transformed MC3T3-E1 cells the JE gene is constitutively expressed at a high level, whereas in their raf-transformed counterparts it is not constitutively expressed or inducible by TPA. Using these cells, we investigated a specific sequence recognized by nuclear factors in the 5'-upstream region of the rat JE gene. By gel-mobility shift assays, we determined that the amount of nuclear factors that bind to the region -130 to -96 bp upstream from the cap site of the rat JE gene (JE-1 probe) increased after TPA treatment of MC3T3-E1 cells. However, in the ras transformants it was elevated constitutively, and in the raf transformants it was not detectable. Both unlabeled JE-1 probe and a probe containing a TPA-responsive element (TGACTCA) competed with the binding of these nuclear factors. Preincubation of the nuclear extracts with fos- or jun-specific antibodies interfered with the binding of the factors to the JE-1 probe. The essential sequence in the JE-1 element for the binding of nuclear factors was found to be TTACTCA. c-fos and c-jun proteins synthesized in vitro could bind to the DNA fragment containing this sequence, but the binding was weaker than to the TPA-responsive element (TGACTCA). These results suggest that the sequence TTACTCA in the JE-1 element is a common target of TPA and ras and that protein complexes containing fos- and jun-related proteins recognize the sequence.

Monocyte chemoattractant protein-1 (MCP-1) expression in human articular cartilage. Induction by peptide regulatory factors and differential effects of dexamethasone and retinoic acid

Monocyte influx and activation in synovial joints are important in the pathogenesis of both degenerative and inflammatory arthropathies. In this study, we demonstrate the potential of articular cartilage to directly modulate these events. IL-1-stimulated human articular chondrocytes transcribed 0.7-kb monocyte chemoattractant protein-1 (MCP-1) mRNA. In situ hybridization of cartilage organ cultures revealed MCP-1 transcripts in chondrocytes in the superficial tangential zone within 2 h of stimulation with IL-1. Chondrocytes in deeper layers responded by 4 h and reached maximum MCP-1 mRNA levels by 8-12 h. IL-1-stimulated cartilage organ and chondrocyte monolayer cultures released functional monocyte chemotactic activity. This was neutralized by a monoclonal antibody specific for MCP-1, and was associated with the synthesis and secretion of immunoreactive 13-kD and 15-kD isoforms of MCP-1. Regulators and signal transduction pathways involved with the expression of the MCP-1 gene in chondrocytes were analyzed. Steady-state mRNA levels were increased by the known chondrocyte activators IL-1, tumor necrosis factor alpha, LPS, platelet-derived growth factor, and transforming growth factor beta. In addition, leukemia inhibitory factor induced MCP-1 gene expression and protein synthesis, identifying this cytokine as a new regulator of chondrocyte function. Dexamethasone blunted the induction of MCP-1 gene expression by IL-1 and by activators of protein kinase A as well as protein kinase C signal transduction pathways. In contrast, retinoic acid strongly increased phorbol myristate acetate-induced MCP-1 expression and potentiated the effects of IL-1 and LPS. In conclusion, chondrocytes express MCP-1 in response to factors that are present in cartilage or synovium. This provides a mechanism by which cartilage can play an active role in the initiation and progression of arthritis.

Enhanced production of monocyte chemoattractant protein-1 in rheumatoid arthritis

Cells within the synovial tissue may recruit mononuclear phagocytes into the synovial fluid and tissues of arthritic patients. We investigated the production of the chemotactic cytokine monocyte chemoattractant protein-1 (MCP-1) using sera, synovial fluid, synovial tissue, as well as macrophages and fibroblasts isolated from synovial tissues from 80 arthritic patients. MCP-1 levels were significantly higher (P less than 0.05) in synovial fluid from RA patients (mean 25.5 +/- 8.1 ng/ml [SE]) compared to synovial fluid from osteoarthritis (OA) patients (0.92 +/- 0.08), or from patients with other arthritides (2.9 +/- 1.5). MCP-1 levels in RA sera (8.44 +/- 2.33) were significantly greater than MCP-1 in normal sera (0.16 +/- 0.06). The quantities of RA synovial fluid IL-8, which is chemotactic for neutrophils and lymphocytes, and MCP-1 were strongly positively correlated (P less than 0.05). To examine the cellular source of MCP-1, RA synovial tissue macrophages and fibroblasts were isolated. Synovial tissue fibroblasts did not express MCP-1 mRNA, but could be induced to produce MCP-1 by stimulation with either IL-1 beta, tumor necrosis factor-alpha (TNF-alpha), or LPS. In contrast, unlike normal peripheral blood monocytes or alveolar macrophages, RA synovial tissue macrophages constitutively expressed MCP-1 mRNA and antigen. Immunohistochemical analysis of synovial tissue showed that a significantly greater percentage of RA macrophages (50 +/- 8%) as compared to either OA macrophages (5 +/- 2) or normal macrophages (1 +/- 0.3) reacted with anti-MCP-1 antibodies. In addition, the synovial lining layer reacted with MCP-1 in both RA and OA synovial tissues. In contrast, only a minority of synovial fibroblasts (18 +/- 8%) from RA synovium were positive for immunolocalization of MCP-1. These results suggest that synovial production of MCP-1 may play an important role in the recruitment of mononuclear phagocytes during inflammation associated with RA and that synovial tissue macrophages are the dominant source of this cytokine.

IL-1 receptor antagonist inhibits monocyte chemotactic peptide 1 generation by human mesangial cells

The elicitation of neutrophils and monocytes from the circulation into the inflamed glomerulus is a key process in the pathogenesis of proliferative glomerulonephritis. The aim of this study was to determine the factors which regulate the expression and synthesis of the monocyte specific chemotaxin, monocyte chemotactic peptide 1 (MCP-1). Mesangial cells in culture did not constitutively express MCP-1, but could be induced to express both MCP-1 mRNA and antigenic MCP-1 by either stimulation with IL-1 alpha or TNF alpha, which are also stimuli for interleukin 8 (IL-8/NAP-1) expression and release. Pre-treatment of mesangial cells with the IL-1 receptor antagonist (IL-1ra) induced dose-dependent inhibition of both the expression of MCP-1 and IL-8 mRNA as well as the release of both chemotactic peptides in response to IL-1 alpha, while the receptor antagonist had no significant effect on TNF alpha induced MCP-1 and IL-8 generation. This study demonstrates that the IL-1 receptor antagonist was four times more effective at inhibiting the IL-1 induced expression and release of IL-8 compared to that of MCP-1. These results suggest that mesangial cell-derived MCP-1 may play an important role in the recruitment of monocytes in glomerular inflammation and that an IL-1 receptor antagonist may have therapeutic potential for the treatment of glomerulonephritis.

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.

Molecular cloning and expression of the murine RANTES cytokine: structural and functional conservation between mouse and man

The infiltration and activation of monocytes is a hallmark of chronic inflammation, including that associated with a variety of disease states such as rheumatoid arthritis, atherosclerosis, and various autoimmune conditions. Recently, a family of small molecular mass proteins has been described which appear to have inflammatory properties, including chemoattractant effects on monocytes. We report here on the molecular cloning, characterization, and functional expression of mu RANTES, a new murine member of this family. mu RANTES expressed in a mammalian expression system is an approximately 8-kDa protein exhibiting immune cross-reactivity with a rabbit polyclonal antiserum generated against human RANTES. Boyden chamber chemotaxis experiments reveal some lack of species specificity in monocyte chemoattractant potential, as recombinant mu RANTES attracts human monocytes in a dose-dependent fashion in vitro. mu RANTES and its human homolog share approximately 85% amino acid identity, a higher level of conservation than that seen with any other species homologs in this cytokine family, and second only to transforming growth factor-beta among reported immune cytokines.

Monocyte chemotactic and activating factor is a potent histamine-releasing factor for basophils

Monocyte chemotactic and activating factor (MCAF) is a recently cloned cytokine that causes chemotaxis of basophils. In our pursuit of cytokines affecting basophil function, we studied the effect of MCAF on histamine secretion from basophils. Leukocytes from 20 donors, 10 allergic and 10 normal subjects, were studied. MCAF caused dose-dependent release of histamine at concentrations of 10(-8) and 10(-7) M, and the mean release was 31.25 +/- 2.9% at the highest concentration. In the same experiments the mean histamine release by anti-IgE and histamine releasing factor (HRF) was 27.05 +/- 4% and 32.70 +/- 2.7%, respectively. All 20 subjects responded to MCAF with significant histamine release. Allergic subjects released significantly more histamine than normals in response to anti-IgE (P less than 0.01) but not to MCAF (P = 0.2) and HRF (P = 0.1). The histamine release was significantly correlated between MCAF and HRF (P less than 0.01), but not between MCAF and anti-IgE (P greater than 0.05). The histamine release by MCAF was complete within the first 3 min. MCAF-induced degranulation was a calcium-dependent process. Leukocytes depleted of monocytes responded equally well to MCAF. Using an anti-MCAF affinity column we determined that greater than 50% of HRF activity of crude PBMC supernatant could be attributed to MCAF. Thus, we established that MCAF is a potent secretagogue for basophils.

G-protein activation by interleukin 8 and related cytokines in human neutrophil plasma membranes

Interleukin 8 (IL-8) is a member of the rapidly growing superfamily of those cytokines which are thought to be involved in the regulation of inflammatory processes and cell proliferation. In neutrophils, IL-8 triggers a variety of cellular responses by interacting with specific cell-surface receptors. To examine whether IL-8 receptors are coupled to activation of guanine-nucleotide-binding proteins (G-proteins), we have investigated the influence of IL-8 on GTP hydrolysis by and guanosine 5'-[gamma-[35S]thio]triphosphate (GTP[35S]) binding to purified human neutrophil plasma membranes. IL-8 stimulated high-affinity GTPase about 2-fold at 100 nM, and half-maximal stimulation was observed at 1 nM. The peptide-stimulated GTPase was confined to plasma membranes upon subcellular fractionation, and was due to an increase in Vmax. rather than a decrease in Km. High-affinity binding of GTP[35S] to neutrophil plasma membranes was stimulated half-maximally and maximally (up to 5-fold) by IL-8 at about 10 nM and 100 nM respectively. GTP[35S] binding to the membranes was also stimulated by two IL-8-related cytokines, neutrophil-activating peptide 2 (NAP-2) and melanoma growth-stimulatory activity (gro/MGSA). Taken together, these results demonstrate that receptors for IL-8 and related cytokines are coupled to and activate G-proteins in neutrophil plasma membranes, indicating that G-protein activation is an important intermediate step in the induction of neutrophil functions by IL-8 and its congeners.

JE mRNA accumulates rapidly in aortic injury and in platelet-derived growth factor-stimulated vascular smooth muscle cells

The early response to vascular injury is characterized by migration of inflammatory cells, including monocytes, and platelets to the damaged vessel wall. These inflammatory cells may serve as a source of growth factors and cytokines that stimulate vascular smooth muscle cell (VSMC) migration and proliferation associated with intimal hyperplasia. JE is a platelet-derived growth factor (PDGF)-inducible "early" gene that encodes a monocyte chemoattractant and, as such, could play an important role in inflammation. We now report that JE mRNA levels are increased in intact aorta after balloon injury. The time course of this increase, with maximal levels at 4 hours, is similar to that seen in PDGF-treated cultured rat aortic VSMCs. The accumulation of JE mRNA in cultured VSMCs is accompanied by a marked increase in the secretion of JE protein. The elevation of JE mRNA levels in VSMCs shows specificity for PDGF, because angiotensin II, alpha-thrombin, and epidermal growth factor fail to increase JE mRNA levels. In contrast to 3T3 fibroblasts, the accumulation of JE mRNA in VSMCs in response to PDGF is predominantly due to an increase in JE mRNA stability. The accumulation of JE mRNA in VSMCs stimulated by PDGF appears to occur via a novel pathway(s) independent of Ca2+ mobilization, Na(+)-H+ exchange, protein kinase C activation, or elevation in cAMP levels. These findings suggest that VSMCs may take part in the early inflammatory response after injury through the production of JE, a potent monocyte chemoattractant. Finally, our data suggest that JE may be a marker for PDGF-specific effects on VSMCs, both in vitro and in vivo. Thus, in addition to direct effects on VSMC growth and migration, PDGF may play a role in the early inflammatory response after vascular injury by inducing chemoattractants, such as that encoded by JE.

A sensitive ELISA for the detection of human monocyte chemoattractant protein-1 (MCP-1)

The recruitment of monocytes into tissue is associated with both acute and chronic inflammation. Although monocyte migration is measured in vitro by monocyte chemotaxis, this technique is often difficult to determine the specific quantitative contribution of a monocyte chemotaxin. We have developed a sensitive sandwich ELISA for the detection of monocyte chemoattractant protein-1 (MCP-1), a highly specific monocyte activating/chemotactic peptide. Polyclonal antibodies were generated from rabbits. The IgG fraction of the antiserum was isolated by a protein A column, with a portion of the antibodies biotinylated. Avidin-conjugated horse radish peroxidase was used for enzymatic, colorimetric analysis. The lower threshold for detection of MCP-1 was 50 pg/ml, and the ELISA was specific for MCP-1, since it failed to recognize other cytokines in a dose-dependent fashion. Furthermore, this ELISA had the capacity to measure endothelial cell and pulmonary fibroblast-derived MCP-1. The development of a sensitive ELISA for the detection MCP-1 is significant, since it will allow the measurement MCP-1 from biologically relevant fluids, and aid in establishing whether MCP-1 is present in disease.