Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Chemokine-protease interactions in cancer

Solid tumour and leukemic cells expressing chemokine receptors, metastasize to chemokine-secreting organs. Chemokines indirectly affect tumour development by attracting immunocompetent cells with pro- or anti-tumoral activities. Various membrane-associated and soluble proteases selectively cleave specific chemokines. Precursor plasma chemokines (CXCL7, CCL14) need to be proteolytically processed to obtain receptor affinity. Angiogenic CXC chemokines (CXCL1, CXCL8) have increased CXCR1/CXCR2 affinity after limited NH2-terminal processing, whereas truncated angiostatic chemokines (CXCL10) show lower CXCR3 affinity without loss of angiostatic potential. NH2-terminally cleaved monocyte chemotactic proteins (CCL2, CCL7, CCL8) have impaired capacity to attract tumour-associated macrophages and function as receptor antagonists for intact CC chemokines. Migration of Th1/CCR5+ and Th2/CCR4+ effector lymphocytes toward CCR5 (CCL5, CCL3L1) and CCR4 (CCL22) ligands is affected by cleavage. Although proteolytical processing of chemokines is well studied in vitro, the direct or indirect effects on tumour invasion and metastasis are only poorly evaluated.

Anti-monocyte chemoattractant protein-1 gene therapy protects against focal brain ischemia in hypertensive rats

Monocyte chemoattractant protein-1 (MCP-1) is expressed in the ischemic cortex after focal brain ischemia and appears to exacerbate ischemic damage. The authors examined the effect of gene transfer of dominant negative MCP-1, called 7ND, 90 minutes after induction of focal brain ischemia in hypertensive rats. Adenoviral vectors encoding mutant MCP-1 (Ad7ND; n = 11), or Escherichia coli beta-galactosidase (AdlacZ; n = 17) as control were injected into the lateral ventricle of male spontaneously hypertensive rats. Both AdlacZ (n = 12) and Ad7ND (n = 6) administration provided transgene expression as early as 6 hours after injection and the expression further increased on day 1, followed by a sustained detection on day 5. Five days after ischemia, infarct volume (75 +/- 13 mm, n = 5, mean +/- SD) significantly reduced to 72% of control (104 +/- 22 mm3, n = 5, P < 0.05) by 7ND gene transfer. Numbers of leukocytes in the vessels (48.3 +/- 32.9/cm2) and macrophage/monocyte infiltration (475.2 +/- 125.5/mm2) of the infarct area in the Ad7ND group were significantly less than those measured in the AdlacZ group (143.8 +/- 72.1/cm2 and 671.8 +/- 125.5/mm2, P < 0.05, respectively). In summary, the postischemic gene transfer of dominant negative MCP-1 attenuated the infarct volume and infiltration of inflammatory cells, suggesting potential usefulness of the anti-MCP-1 gene therapy.

CCR2-dependent trafficking of F4/80dim macrophages and CD11cdim/intermediate dendritic cells is crucial for T cell recruitment to lungs infected with Mycobacterium tuberculosis

We previously reported that CCR2(-/-) mice are susceptible to Mycobacterium tuberculosis infection. Susceptibility was associated with an early and sustained macrophage trafficking defect, followed by delayed recruitment of dendritic cells (DCs) and T cells to the lungs. However, the relative importance of the lack of CCR2 expression by macrophages and DCs vs T cells in susceptibility to infection was unclear. In this study, we used mixed bone marrow transplantation to create mice in which the genotype of the T cells was either CCR2(+/+) or CCR2(-/-) while maintaining the genotype of the myeloid cells as CCR2(+/+). After infection with M. tuberculosis, we found that the genotype of the macrophages and/or DCs, but not that of the T cells, was critical for both T cell and myeloid cell migration to the lungs. Further investigation revealed a critical role for CCR2 in the recruitment of F4/80(dim) macrophages and CD11c(dim/intermediate) DCs to the infected lung.

Aspergillus antigen induces robust Th2 cytokine production, inflammation, airway hyperreactivity and fibrosis in the absence of MCP-1 or CCR2

BACKGROUND

Asthma is characterized by type 2 T-helper cell (Th2) inflammation, goblet cell hyperplasia, airway hyperreactivity, and airway fibrosis. Monocyte chemoattractant protein-1 (MCP-1 or CCL2) and its receptor, CCR2, have been shown to play important roles in the development of Th2 inflammation. CCR2-deficient mice have been found to have altered inflammatory and physiologic responses in some models of experimental allergic asthma, but the role of CCR2 in contributing to inflammation and airway hyperreactivity appears to vary considerably between models. Furthermore, MCP-1-deficient mice have not previously been studied in models of experimental allergic asthma.

METHODS

To test whether MCP-1 and CCR2 are each required for the development of experimental allergic asthma, we applied an Aspergillus antigen-induced model of Th2 cytokine-driven allergic asthma associated with airway fibrosis to mice deficient in either MCP-1 or CCR2. Previous studies with live Aspergillus conidia instilled into the lung revealed that MCP-1 and CCR2 play a role in anti-fungal responses; in contrast, we used a non-viable Aspergillus antigen preparation known to induce a robust eosinophilic inflammatory response.

RESULTS

We found that wild-type C57BL/6 mice developed eosinophilic airway inflammation, goblet cell hyperplasia, airway hyperreactivity, elevations in serum IgE, and airway fibrosis in response to airway challenge with Aspergillus antigen. Surprisingly, mice deficient in either MCP-1 or CCR2 had responses to Aspergillus antigen similar to those seen in wild-type mice, including production of Th2 cytokines.

CONCLUSION

We conclude that robust Th2-mediated lung pathology can occur even in the complete absence of MCP-1 or CCR2.

Chemokines and glial cells: a complex network in the central nervous system

Chemokines are small secreted proteins that are essential for the recruitment and activation of specific leukocyte subsets at sites of inflammation and for the development and homeostasis of lymphoid and nonlymphoid tissues. During the past decade, chemokines and their receptors have also emerged as key signaling molecules in neuroinflammatory processes and in the development and functioning of the central nervous system. Neurons and glial cells, including astrocytes, oligodendrocytes, and microglia, have been identified as cellular sources and/or targets of chemokines produced in the central nervous system in physiological and pathological conditions. In this article, we provide an update of chemokines and chemokine receptors expressed by glial cells focusing on their biological functions and implications in neurological diseases.

Expression profiles of genes involved in the mouse nuclear factor-kappa B signal transduction pathway are modulated by mangiferin

The polyphenol mangiferin (MA) has been shown to have various effects on macrophage function, including inhibition of phagocytic activity and of free radical production. To further characterize the immunomodulatory activity of MA, this study investigated its effects on expression by activated mouse macrophages of diverse genes related to the NF-kappaB signaling pathway, using a DNA hybridization array containing 96 NF-kappaB-related genes and on cytokine levels using a cytokine protein array. MA at 10 microM significantly inhibited the expression of (a) two genes of the Rel/NF-kappaB/IkappaB family, RelA and RelB (=I-rel), indicating an inhibitory effect on NF-kappaB-mediated signal transduction; (b) TNF receptor-associated factor 6 (Traf6), indicating probable blockage of activation of the NF-kappaB pathway by lipopolysaccharide (LPS), tumor necrosis factor (TNF), and interleukin 1 (IL-1); (c) other proteins involved in responses to TNF and in apoptotic pathways triggered by DNA damage, including the TNF receptor (TNF-R), the TNF-receptor-associated death domain (TRADD), and the receptor interacting protein (RIP); (d) the extracellular ligand IL-1alpha, again indicating likely interference with responses to IL-1; (e) the pro-inflammatory cytokines IL-1, IL-6, IL-12, TNF-alpha and RANTES (CCL5), and cytokines produced by monocytes and macrophages, including granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF); (f) other toll-like receptor proteins (in addition to Traf6), including JNK1, JNK2 and Tab1; (g) Scya2 (small inducible cytokine A2=monocyte chemoattractant protein 1); and (h) various intracellular adhesion molecules (ICAMs), and the vascular cell adhesion molecule VCAM-1, which is locally increased in atheromas. The inhibition of JNK1, together with stimulation of c-JUN (i.e. the Jun oncogene) and the previously reported superoxide-scavenging activity of MA, suggests that MA may protect cells against oxidative damage and mutagenesis. Taken together, these results indicate that MA modulates the expression of a large number of genes that are critical for the regulation of apoptosis, viral replication, tumorogenesis, inflammation and various autoimmune diseases, and raise the possibility that it may be of value in the treatment of inflammatory diseases and/or cancer.

Increased expression of cytokines and adhesion molecules in rat chronic esophagitis

BACKGROUND/AIMS

Cytokines and adhesion molecules regulate many inflammatory processes in several gastrointestinal diseases. The dynamics of cytokines and adhesion molecules in reflux esophagitis are unknown in detail. We examined the expression and dynamics of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-2, GRO/cytokine-induced neutrophil chemoattractant-2alpha (CINC-2alpha), intercellular adhesion molecule-1 (ICAM-1), leukocyte function-associated antigen 1 (LFA-1; CD11a/CD18), and Mac-1 (CD11b/CD18) in rat chronic reflux esophagitis.

METHODS

Chronic acid reflux esophagitis was induced in Wistar rats by ligating the transitional region between the forestomach and the glandular portion and wrapping the duodenum near the pylorus with a small piece of an 18-Fr Nélaton catheter. Rats were killed 3 or 21 days after operation. The levels of mRNA expression of cytokines and ICAM-1 were determined by real-time quantitative RT-PCR. Localization of adhesion molecules and cytokines was investigated by immunohistochemical staining, and numbers of LFA-1- or Mac-1-positive cells were quantified.

RESULTS

IL-1beta, TNF-alpha, MCP-1, MIP-1alpha, MIP-2, CINC-2alpha, and ICAM-1 mRNA expression was significantly increased in esophageal lesions compared with normal esophagus. There were few these cytokines- or adhesion molecule-positive cells in normal esophagus. In regions of esophagitis, numerous inflammatory leukocytes in lamina propria and the submucosal layer exhibited positive reactions for these cytokines and endothelial cells were intensely stained for ICAM-1. Numbers of LFA-1- and Mac-1-positive cells were significantly increased in rat chronic esophagitis. Treatment with rabeprazole almost completely inhibited development of chronic acid reflux esophagitis and significantly decreased expression of cytokines and ICAM-1 mRNA in esophageal tissue compared with control.

CONCLUSION

Cytokines and adhesion molecules play important roles in the pathogenesis of chronic reflux esophagitis in this rat model.

Serum monocyte chemoattractant protein-1 in patients with postoperative infectious complications from gastrointestinal surgery for cancer

We examined the kinetics of serum monocyte chemoattractant protein-1 (MCP-1) perioperatively and clarified its significance regarding the development of infectious complications. We studied 94 patients who underwent gastrointestinal surgery for gastric or colorectal cancer at Mie University Hospital from 1996 to 2000. Serum concentrations of MCP-1 and interleukin-6 (IL-6) were measured perioperatively. The number of circulating lymphocytes and neutrophils were counted to assess the apoptotic rate of neutrophils. Patients were divided into two groups at the median preoperative MCP-1 level obtained from 40 gender- and age-matched healthy volunteers. The rate of developing infectious complications was significantly higher and tumor size was significantly larger in the low MCP-1 group than in the high MCP-1 group. The increasing IL-6 ratio (postoperative/preoperative IL-6 level) in the low MCP-1 group was about twofold greater than that in the high MCP-1 group. The neutrophil level calculated for the low MCP-1 group was significantly higher than that in the high MCP-1 group on postoperative day 3. We concluded that a decreased level of serum MCP-1 reflected tumor-related immunosuppression. Low MCP-1 levels were associated with an exaggerated postoperative IL-6 response and delayed neutrophil apoptosis, which affected the incidence of postoperative infectious complications developing in patients with gastrointestinal malignancies.

Sequential MyD88-independent and -dependent activation of innate immune responses to intracellular bacterial infection

Microbial infections induce chemokine and cytokine cascades that coordinate innate immune defenses. Infection with the intracellular bacterial pathogen Listeria monocytogenes induces CCR2-dependent monocyte recruitment and activation, an essential response for host survival. Herein we show that invasive L. monocytogenes, but not killed or noninvasive bacteria, induce secretion of MCP-1, the requisite chemokine for monocyte recruitment. Induction of MCP-1, but not TNF or IL-12, following L. monocytogenes infection is MyD88 independent. Consistent with these results, MyD88 deficiency does not impair monocyte recruitment to L. monocytogenes infected spleens, but prevents monocyte activation. Our results indicate that distinct microbial signals activate innate immune responses in an ordered, step-wise fashion, providing a mechanism to specify and modulate antimicrobial effector functions.

C-C chemokine receptor 2 and sarcoidosis: association with Lofgren's syndrome

Sarcoidosis is thought to result from the interaction between an unknown environmental antigenic trigger and the host's genetic susceptibility. We hypothesized that sarcoidosis, or one of the disease subsets, could be associated with single nucleotide polymorphisms of C-C chemokine receptor 2 (CCR2) gene. Eight single-nucleotide polymorphisms in CCR2 were studied in a total of 304 Dutch individuals (90 non-Löfgren sarcoidosis, 47 Löfgren's syndrome, 167 control subjects). From the investigated CCR2 polymorphisms, nine haplotypes were deduced (haplotypes 1-9). In patients with Löfgren's syndrome, a strongly significant increase in the frequency of CCR2-haplotype 2, which includes four unique alleles (A at nucleotide position -6752, A at 3,000, T at 3,547, and T at 4,385), was observed compared with control subjects (74% vs. 38% respectively, p < 0.0001), whereas no difference was found between non-Löfgren sarcoidosis and control subjects (both 38%). The association between CCR2-haplotype 2 carriage frequency and Löfgren's syndrome (odds ratio, 4.4; p < 0.0001) remained significant after adjustment for human leukocyte antigen haplotype DRB1*0301-DQB1*0201 (odds ratio, 11.5; p < 0.0001) and female sex (odds ratio, 3.2; p = 0.003), two known risk factors for Löfgren's syndrome. In conclusion, this report describes a strong association between CCR2-haplotype 2 and Löfgren's syndrome. Further studies are needed to understand the molecular mechanisms underlying this association.

Differential effects of staurosporine and its analogues on chemokine release by promyelocytic leukemia cell line NB-4

The protein kinase inhibitor staurosporine elicits multiple responses in various systems. We evaluated nine naturally occurring staurosporine derivatives as modulators of chemokine production by monitoring the secretion of interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) in the cell line NB-4. Several staurosporines increased, dose- and time-dependently, the IL-8 and MCP-1 concentration in the cell culture supernatants and three derivatives strongly inhibited proliferation of the NB-4 cells. By comparing the efficiency of these analogues at the same concentration, the lead compound staurosporine (STS-1) was the best inducer of chemokine secretion, whereas 3-hydroxystaurosporine (STS-3) was the most potent growth inhibitor. Besides the staurosporines, also 12-O-tetradecanoyl phorbol acetate (TPA) and tumor necrosis factor-alpha (TNFalpha) strongly increased the IL-8 and MCP-1 secretion of NB-4 cells. Several staurosporine analogues clearly inhibited the TPA-induced but enhanced the TNFalpha-mediated chemokine increase. These effects, namely the increase of chemokines in untreated or TNFalpha-treated cells and the inhibition of chemokine release in TPA-treated cells, cannot be explained by the exclusive inhibition of protein kinase C (PKC). It may indicate that staurosporines are additionally involved in activation of the PKC-triggered chemokine production.

Overexpression of monocyte chemoattractant protein 1 in the brain exacerbates ischemic brain injury and is associated with recruitment of inflammatory cells

Brain cells produce cytokines and chemokines during the inflammatory process after stroke both in animal models and in patients. Monocyte chemoattractant protein 1 (MCP-1), one of the proinflammatory chemokines, can attract monocytes to the tissue where MCP-1 is overexpressed. However, the role of MCP-1 elevation in stroke has not been explored in detail. The authors hypothesized that elevated MCP-1 levels would lead to increased influx of monocytes and increased brain infarction size in stroke induced by middle cerebral artery occlusion with partial reperfusion. There were no differences in blood pressure, blood flow, or vascular architecture between wild-type mice and transgenic MBP-JE mice. Twenty-four to 48 hours after middle cerebral artery occlusion, brain infarction volumes after ischemia were significantly larger in MBP-JE mice than in wild-type controls and were accompanied by increased local transmigration and perivascular accumulation of macrophages and neutrophils. These results indicate that MCP-1 can contribute to inflammatory injury in stroke.

Monocyte chemoattractant protein-1 (CCL2) in inflammatory disease and adaptive immunity: therapeutic opportunities and controversies

Monocyte chemoattractant protein (MCP)-1 (CCL2) specifically attracts monocytes and memory T cells. Its expression occurs in a variety of diseases characterized by mononuclear cell infiltration, and there is substantial biological and genetic evidence for its essential role in atherosclerosis and multiple sclerosis. Despite intensive screening, there are as yet no small-molecule antagonists of the receptor of MCP-1/CCL2, CCR2. However, biological agents, including antibodies and inhibitory peptides, have been developed and may be useful for these indications. Recent evidence from genetically modified mice indicates that MCP-1 and CCR2 have unanticipated effects on T helper (Th) cell development. However, unlike the identical phenotypes of MCP-1/CCL2(-/-) and CCR2(-/-) mice in inflammatory diseases, the phenotypes of these mice are disparate in adaptive immunity: MCP-1 stimulates Th2 polarization, whereas CCR2 activation stimulates Th1 polarization. This presents both a challenge and an opportunity for targeting the MCP-1/CCL2/CCR2 axis in disease.

Host microenvironment in breast cancer development: inflammatory and immune cells in tumour angiogenesis and arteriogenesis

Breast cancer progression is associated with and dependent upon robust neovascularization. It is becoming clear that tumour-associated 'normal' cells, such as immune/inflammatory cells, endothelial cells and stromal cells, conspire with cancer cells in promoting this process. In particular, infiltrating immune/inflammatory cells secrete a diverse repertoire of growth factors and proteases that enable them to enhance tumour growth by stimulating angiogenesis and, as we suggest here, by promoting 'tumour arteriogenesis' - enlargement of feeding vessels supplying the expanding tumour capillary bed. Macrophages and their chemoattractants (e.g. macrophage chemoattractant protein-1) are critical for the arteriogenic process in ischaemia, and probably also in breast neoplasia. A better understanding of these various cellular and molecular constituents of breast cancer neovascularization may be useful in designing more effective therapies.

Redirecting migration of T cells to chemokine secreted from tumors by genetic modification with CXCR2

T-cell-based immunotherapies provide a promising means of cancer treatment although durable antitumor responses are infrequent. A potential reason for these shortcomings may lie in the observed lack of trafficking of specific T cells to tumor. Our increasing knowledge of the process of trafficking involving adhesion molecules and chemokines affords us the opportunity to intervene and correct deficiencies in this process. Chemokines can be expressed by a range of tumors and may serve as suitable targets for directing specific T cells toward tumor. We initially sought to identify which chemokines were produced by a range of human tumor cell lines, and which chemokines and chemokine receptors were expressed by cultured T cells. We identified two chemokines: Growth-Regulated Oncogene-alpha (Gro-alpha; CXCL1) and Regulated on Activation Normal T Cell-Expressed and Secreted (RANTES; CCL5), to be secreted by several human tumor cell lines. Expression was also detected in fine-needle aspirates of melanoma from patients. In addition, we determined the expression of several chemokine receptors on cultured human T cells including CCR1, CCR2, CCR4, CCR5, CXCR3, and CXCR4. Cultured, activated human T cells expressed the chemokines lymphotactin (XCL1), RANTES, macrophage inflammatory protein-1 alpha (MIP-1 alpha; CCL3) and MIP-1 beta (CCL4), but no appreciable Gro-alpha. In a strategy to direct T cells toward chemokines expressed by tumors we chose Gro-alpha as the target chemokine because it was produced by tumor and not by T cells themselves. However, T cells did not express the receptor for Gro-alpha, CXCR2, and therefore, T cells were transduced with a retroviral vector encoding CXCR2. Calcium ion mobilization, an important first step in chemokine receptor signaling, was subsequently demonstrated in transduced T cells in response to Gro-alpha. In addition, Gro-alpha was chemotactic for T cells expressing CXCR2 in vitro toward both recombinant protein and tumor-derived chemokine. Interestingly we demonstrate, for the first time, that Gro-alpha was able to induce interferon-gamma (IFN-gamma) secretion from transduced T cells, thereby extending our knowledge of other potential functions of CXCR2. This study demonstrates the feasibility of redirecting the migration properties of T cells toward chemokines secreted by tumors.

Vascular endothelial growth factor induces chemotaxis and proliferation of microglial cells

Vascular endothelial growth factor (VEGF) is an angiogenic peptide that is produced in the brain after ischemia, injury or in malignant gliomas. Since these pathological conditions are associated with the infiltration of microglial cells, we investigated the expression of VEGF receptors (VEGFR) and possible effects of VEGF on cultivated microglial cells. As shown by reverse transcription-polymerase chain reaction and immunocytochemistry, rat microglial cells as well as the murine cell line BV-2 express the VEGFR-1, but not VEGFR-2. Murine VEGF induced 3H-thymidine incorporation into DNA of murine and rat microglial cells as well as chemotaxis in Boyden chamber assays. However, VEGF did not alter the phosphorylation of mitogen-activated protein kinases and only slightly that of the kinase Akt. These results show that microglial cells are targets for VEGF which induces migration and proliferation of these immunocompetent cells in the brain.

Characterization of chemokines and their receptors in the central nervous system: physiopathological implications

Chemokines represent key factors in the outburst of the immune response, by activating and directing the leukocyte traffic, both in lymphopoiesis and in immune surveillance. Neurobiologists took little interest in chemokines for many years, until their link to acquired immune deficiency syndrome-associated dementia became established, and thus their importance in this field has been neglected. Nevertheless, the body of data on their expression and role in the CNS has grown in the past few years, along with a new vision of brain as an immunologically competent and active organ. A large number of chemokines and chemokine receptors are expressed in neurons, astrocytes, microglia and oligodendrocytes, either constitutively or induced by inflammatory mediators. They are involved in many neuropathological processes in which an inflammatory state persists, as well as in brain tumor progression and metastasis. Moreover, there is evidence for a crucial role of CNS chemokines under physiological conditions, similar to well known functions in the immune system, such as proliferation and developmental patterning, but also peculiar to the CNS, such as regulation of neural transmission, plasticity and survival.

MCP-1 and RANTES are expressed in renal cortex of rats chronically treated with nitric oxide synthase inhibitor. Involvement in macrophage and monocyte recruitment

Long-term inhibition of nitric oxide synthase (NOS) in rats is known to cause systemic hypertension and renal parenchymal injury. We have previously reported that activation of intra-renal renin-angiotensin system was a major contributing factor for renal injury in chronically NOS-inhibited rats. Massive interstitial infiltration of monocytes/macrophages (M/M) was characteristically seen in this model. The present study was performed to elucidate the role of chemokines, RANTES and MCP-1, in promoting M/M recruitment into the renal cortex. The number of infiltrating ED-1-positive cells was examined in association with the level of expression of RANTES and MCP1 mRNAs in the renal cortex of rats treated orally for 12 weeks with L-NAME. Compared to controls rats, the number of infiltrating ED-1-positive cells was significantly higher in L-NAME-treated rats. The mRNA expressions of both RANTES and MCP-1 were significantly higher in L-NAME-treated rats than the control. In L-NAME-treated rats, the high number of ED-1-positive cells and increased expression of both RANTES and MCP-1 were suppressed by ACE inhibitor, but not by hydralazine. In contrast, neither ED-1 counts nor RANTES mRNA expression were affected by angiotensin (Ang) II type 1 receptor antagonist. These results suggest the likely involvement of RANTES and MCP-1 in the recruitment of M/M into the renal cortex of rats with chronic NOS inhibition. Furthermore, it is also indicated that Ang II stimulates MCP-1 expression via Ang II type 1 receptor, whereas RANTES expression is mediated via Ang II type 2 receptor.

Tumor-associated macrophages: a molecular perspective

The "macrophage balance hypothesis" was proposed in the early 1990s to depict the complex relationship that tumor-associated macrophages (TAM) have with the neoplastic cells of the tumor. TAM represent a prominent component of the mononuclear leukocyte population of solid tumors, which displays an ambivalent relationship with tumors. They originate in the circulation and are recruited to the tumor site by tumor-derived attractants such as chemokines and interact with the tumor cells and preferentially localize at the tumor-host tissue interface, in regions often associated with low oxygen tensions. The tumor microenvironment, including cytokines and hypoxia, regulates the localization and function of TAM. Emerging evidence starts to define the molecular basis for the peculiar functional phenotype of TAM and identifies possible therapeutic targets.

Tyrosine phosphorylation-mediated signal transduction in MCP-1-induced macrophage activation: role for receptor dimerization, focal adhesion protein complex and JAK/STAT pathway

Monocyte chemoattractant protein-1 (MCP-1) plays a crucial role in the recruitment of monocytes/macrophages associated with several inflammatory diseases and malignancies. The early signal transduction mechanism of macrophage activation in response to in vitro MCP-1 treatment was investigated. The treatment of murine peritoneal macrophages with MCP-1 resulted in a significant enhancement in the tyrosine phosphorylation of cellular proteins, which peaked within 2.5-5 min of MCP-1 treatment. The MCP-1-induced tyrosine phosphorylation of cellular proteins involved the phosphorylation of non-receptor tyrosine kinases Lyn, JAK2, cytoskeletal binding protein paxillin and downstream transcription factors STAT3 and STAT5. Immunoflourescence microscopical studies on MCP-1-treated macrophages showed the cellular localization of the tyrosine-phosphorylated proteins and bundling of actin filaments at the focal adhesion points. MCP-1-induced association of focal adhesion proteins Lyn/phospho-paxillin with CCR2 was also observed by co-precipitation. Inhibitor studies with genistein on MCP-1-induced macrophage TNF and IL-1 production additionally supported the role of protein tyrosine phosphorylation in the process of macrophage activation with MCP-1. Present investigations suggest that the early events in the tyrosine kinase signal transduction pathway for macrophage activation in response to MCP-1 probably involve (1) CCR2 receptor dimerization, (2) enhanced tyrosine phosphorylation and assembly of focal adhesion complex, and (3) the activation of JAK/STAT pathway in the murine peritoneal macrophages.

In vitro activation of murine peritoneal macrophages by monocyte chemoattractant protein-1: upregulation of CD11b, production of proinflammatory cytokines, and the signal transduction pathway

The CC chemokine monocyte chemotactic protein-1 (MCP-1) is a major mediator of monocyte/macrophage infiltration at the inflammatory sides under both physiologic and pathologic conditions. We report the ability of MCP-1 to activate murine peritoneal macrophages in vitro for enhanced expression of CD11b, macrophage-mediated cytotoxicity, and production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). The macrophages treated with MCP-1 in vitro displayed significant cytolytic activity toward TNF-alpha-sensitive L929 cells in a dose-dependent manner. The macrophage-mediated L929 cytotoxicity was blocked in the presence of anti-TNF-alpha antibodies, suggesting the involvement of TNF-alpha. Production of TNF-alpha and IL-1 macrophages on MCP-1 treatment was maximum at 24 h of incubation with 100 ng/ml MCP-1. Enhanced TNF-alpha and IL-1beta mRNA expression was also demonstrated by RT-PCR, which revealed transcription of interferon gamma (IFN-gamma), IL-12, and related T cell-specific chemokine genes, KC and IP-10, in the MCP-1-treated macrophages. The pharmacologic inhibitors pertussis toxin (100 ng/ml), wortmannin (200 ng/ml), H-7 (10 microM), PD98059 (25 microM), and genistein (10 microg/ml) significantly inhibited TNF-alpha and IL-1 production in the MCP1-treated macrophages, suggesting the involvement of G-proteins, phosphoinositol-3-kinase (PI3K), protein kinase C, p42/44 MAPK, and tyrosine kinases in this process.

The role of chemokines in human cardiovascular pathology: enhanced biological insights

A growing body of experimental evidence supports the pivotal role of chemokines in the pathogenesis of vascular disease. The endothelial expression of monocyte chemoattractant protein-1 (MCP-1) is apparently essential for the earliest cellular responses of atherogenesis. Many atherogenic and anti-atherogenic stimuli can be construed to exert their effects predominantly upon MCP-1 expression within the vascular wall. The atherogenic effects of interleukin-8 (IL-8) seem to be mediated through the down-regulation of the tissue inhibitor of metalloproteinase-1 (TIMP-1). Biological expression of these two important vascular chemokines is further modulated by NF-kappaB. The delineation of these molecular forces that drive atherogenesis increasingly underscores the pivotal role of various chemokines. It is anticipated that more precise delineation of these patterns of gene expression will help to identify molecular targets for the prevention and treatment of atherosclerosis.

Human pancreatic islets produce and secrete MCP-1/CCL2: relevance in human islet transplantation

We investigated the capacity of human islets to produce monocyte chemoattractant protein-1 (MCP-1). Primary cultures of pancreatic islets expressed and secreted MCP-1, as determined by Northern blot, immunohistochemistry, in situ hybridization, and enzyme-linked immunosorbent assay. The produced MCP-1 was biologically active as it attracted monocytes in chemotaxis assay, and chemotactic activity was almost abrogated by a neutralizing anti-MCP-1 monoclonal antibody. Expression of MCP-1 was increased by primary inflammatory cytokines (interleukin-1 beta, tumor necrosis factor-alpha) and lipopolysaccharide at both the mRNA and protein levels but not by glucose. However, MCP-1 did not modulate insulin secretion. MCP-1 secreted by pancreatic islets plays a relevant role in the clinical outcome of islet transplant in patients with type 1 diabetes. In fact, low MCP-1 secretion resulted as the most relevant factor for long-lasting insulin independence. This finding opens new approaches in the management of human islet transplantation. Finally, the finding that MCP-1 appears constitutively present in normal human islet beta-cells (immunohistochemistry and in situ hybridization), in the absence of an inflammatory infiltrate, suggests that this chemokine could have functions other than monocyte recruitment and opens a new link between the endocrine and immune systems.

MCP-1 modulates chemotaxis by follicular lymphoma cells

The localization and establishment of follicular lymphoma (FL) cells in distinct anatomic sites probably involves chemokine and adhesion receptors on the neoplastic cells and appropriate chemokines and adhesion receptor ligands in the microenvironment. Several chemokines play an important role in normal B-cell trafficking and differentiation. Monocyte chemoattractant protein-1 (MCP-1) is a C-C chemokine that induces chemotaxis of a variety of lymphoid cells through its receptor CCR2. CCR2 is also expressed on B cells, and MCP-1 induces chemotaxis of normal B cells. In this report, we investigated expression and function of CCR2 on FL cells. We found FL cells as well as the t(14; 18)+ B-cell lymphoma line H2 expressed CCR2. MCP-1 potentiated SDF-1-induced chemotaxis of FL cells and H2 cells, but MCP-1 alone did not induce chemotaxis. The specificity of the effects of MCP-1 and SDF-1 was demonstrated by antibody blocking studies. Because FL cells are generally associated with follicular dendritic cells (FDCs), FDCs may be an important source of chemokines. We found that cultured FDCs produced MCP-1, and this production was enhanced by tumour necrosis factor. These data implicate MCP-1 in the migration and localization of FL cells.

Fas ligand engagement of resident peritoneal macrophages in vivo induces apoptosis and the production of neutrophil chemotactic factors

Fas ligand (FasL) is a potent proapoptotic type-II transmembrane protein that can cause cell death in Fas+ target populations. Despite the presumed "silent" nature of apoptotic cell death, forced expression of FasL can induce a dramatic inflammatory response. To elucidate the in vivo mechanism(s) linking FasL and inflammation, we used a membrane-bound cell-free form of FasL (mFasL-vesicle preparation (VP)). We found that i.p. injection of FasL-microvesicles led to the rapid activation and subsequent demise of Mac1(high) resident peritoneal macrophages. Apoptosis of Mac1(high) peritoneal macrophages was observed within 0.5 h of mFasL-VP injection and correlated with the detection of increased macrophage inflammatory protein (MIP)-2 levels in peritoneal lavage fluid as well as induced RNA expression of IL-1beta, MIP-2, MIP-1alpha, and MIP-1beta. In vitro culture of purified peritoneal populations identified Mac1(high) cells as the major cytokine/chemokine producers in response to mFasL-VP. Purified Mac1(high) cells exposed to FasL could restore the ability of Fas-deficient mice to mount an inflammatory response. Our data demonstrate that the FasL-mediated inflammatory response starts with the production of proinflammatory mediators by preapoptotic resident tissue macrophages and suggest a general mechanism responsible for neutrophil inflammation seen in cases of FasL-expressing allografts.

Identification of new regulatory sequences far upstream of the mouse monocyte chemoattractant protein-1 gene

We systematically searched for sequences influencing the expression of the mouse monocyte chemoattractant protein-1 (MCP-1) gene (Scya2) by mapping DNase I hypersensitive sites (HS) in the chromatin of mesangial cells in a 40-kb interval around the gene. We found nine HS located between -24 kb and +12.7 kb. Three HS coincided with previously known regulatory sequences (HS-2.4, HS-1.0, and HS-0.2). We tested two of the previously unknown HS located far upstream of Scya2 (HS-19.4 and HS-16.3) in transfection experiments using luciferase reporter constructs and mouse mesangial cells as recipients. In transient transfections, both HS had a moderate effect on basal promoter activity as well as promoter activity stimulated by tumor necrosis factor-alpha. In stable transfection experiments, we found much higher activity. A DNA fragment containing HS-19.4 and HS-16.3 caused a considerable increase in the number of stably integrated luciferase copies. We determined the nucleotide sequence of the 5' flanking region to -28.6 kb. Computer-assisted sequence analysis did not yield evidence of an additional gene. These HS are located within the 5' flanking region of a gene cluster consisting of Scya2 (MCP-1), Scya7 (MCP-3), Scya11 (eotaxin), Scya12 (MCP-5), and Scya8 (MCP-2). This report represents the first comprehensive chromatin analysis of the mouse MCP-1 locus leading to the identification of a complex regulatory region located far upstream of Scya2.

The viral CC chemokine-binding protein vCCI inhibits monocyte chemoattractant protein-1 activity by masking its CCR2B-binding site

Monocyte chemoattractant protein-1 (MCP-1) is a chemotactic cytokine mainly acting on monocytes and T cells that elicits its biological effects by interacting with the seven-transmembrane helix receptor CCR2B. The vaccinia virus strain Lister and many other poxviruses express soluble proteins (vCCI) that bind MCP-1 and other CC chemokines and inhibit their function. In order to define the interaction site of MCP-1 with vCCI from vaccinia, surface exposed residues of MCP-1 were identified and mutated to alanine. The MCP-1 variants were expressed, purified, and their interaction with vCCI was characterized. The site on MCP-1 for vCCI binding is dominated by arginine 18 with important additional contributions from tyrosine 13 and arginine 24. These residues define a binding site that largely overlaps with the CCR2B receptor interaction site. The viral chemokine-binding protein vCCI thus inhibits the biological function of MCP-1 by directly masking its CCR2B receptor-binding site.

Expression of Fas ligand by microglia: possible role in glioma immune evasion

The immune-privileged status of the central nervous system is thought to limit the application of immunotherapy for treatment of malignant brain tumors. Because the Fas pathway has been proposed to play a role in immune evasion, we examined the effect of tumor environment on the expression of Fas ligand (FasL) in a mouse glioma model. Immunoblotting revealed the expression of membrane-bound FasL to nearly double when murine G26 gliomas were propagated intracranially (IC) as compared to subcutaneously (SC). Further analysis by flow cytometry revealed microglia, which were absent in the SC tumors, to account for half of the FasL expression in the IC tumors. Interestingly, when FasL activity was inhibited in IC tumors, the proportion of tumor-infiltrating leukocytes increased three-fold, reaching the same frequency as the SC tumors. These observations suggest that microglia are a major source of FasL expression in brain tumors and possibly contribute to the local immunosuppressive milieu of malignant gliomas.

Significant correlation of monocyte chemoattractant protein-1 expression with neovascularization and progression of breast carcinoma

BACKGROUND

Macrophages often infiltrate into solid tumor tissues. Tumor-associated macrophages (TAMs) are known to play a crucial role in tumor progression. Monocyte chemoattractant protein-1 (MCP-1) is one of the major chemokines capable of inducing chemotactic migration of monocytes.

METHODS

With the objective of investigating the clinical significance of MCP-1, the authors analyzed the expression of MCP-1 and of some other molecules by immunohistochemistry in 230 samples of primary breast carcinoma tissue. MCP-1 staining was performed using an anti-MCP-1 monoclonal antibody, and it was assessed by grading the percentage of stained cells.

RESULTS

It was found that 117 breast tumor specimens (51%) had intensive staining in tumor cells. The expression of MCP-1 in tumor cells had a significant correlation with the expression of thymidine phosphorylase and membrane type 1-matrix metalloproteinase. In addition, MCP-1 expression tended to be associated with the accumulation of TAMs, which were counted by CD68 staining, and with microvessel density. MCP-1 expression in TAMs was correlated significantly with the histologic vessel invasion of tumor cells.

CONCLUSIONS

The results of this study suggest that MCP-1 may play key roles in macrophage recruitment, in the expression of angiogenic factors, and in the activation of matrix metalloproteinases in patients with breast carcinoma.

Chemokines in patients with ischaemic heart disease and the effect of coronary angioplasty

Percutaneous coronary transluminal angioplasty (PTCA) may release inflammatory mediators such as chemokines. Monocyte chemoattractant protein-1 (MCP-1) and eotaxin (EOX) are monocyte- and eosinophil-specific chemokines involved in the inflammation and pathogenesis of coronary atherosclerosis. A total of 28 patients undergoing elective PTCA, 20 coronary artery disease (CAD) patients undergoing coronary angiography and 28 healthy controls were studied. In PTCA patients before the procedure, MCP-1 plasma levels (441+/-64 pg/ml) were similar to those of CAD patients (430+/-24 pg/ml), and significantly higher compared with controls (145+/-17 pg/ml, P<0.01). MCP-1 rose significantly after 3 and 6 months following PTCA (696+/-89 and 876+/-86 pg/ml, respectively, P<0.01 vs. before PTCA). EOX plasma levels (155+/-14 pg/ml) were similar to those of CAD patients (157+/-14 pg/ml), but significantly higher compared with controls (83.2+/-10 pg/ml, P<0.05). EOX rose significantly 24 h (273+/-41 pg/ml, P<0.05) but not 3 months after PTCA (160+/-20 and 158+/-19 pg/ml, respectively). These findings indicate that chemokine-induced monocyte- and eosinophil-specific chemoattraction is stimulated in patients with coronary artery disease. MCP-1 levels remain significantly elevated for at least 6 months following elective PTCA, suggesting an inflammatory stimulation.

Role of microglia in glioma biology

Microglia, a type of differentiated tissue macrophage, are considered to be the most plastic cell population of the central nervous system (CNS). In response to pathological conditions, resting microglia undergo a stereotypic activation process and become capable of phagocytosis, antigen presentation, and lymphocyte activation. Considering their immune effector function, it is not surprising to see microglia accumulation in almost every CNS disease process, including malignant brain tumors or malignant gliomas. Although the function of these cells in CNS inflammatory processes is being studied, their role in malignant glioma biology remains unclear. On one hand, microglia may represent a CNS anti-tumor response, which is inactivated by local secretion of immunosuppressive factors by glioma cells. On the other hand, taking into account that microglia are capable of secreting a variety of immunomodulatory cytokines, it is possible that they are attracted by gliomas to promote tumor growth. A better understanding of microglia-glioma interaction will be helpful in designing novel immune-based therapies against these fatal tumors.

Chemokine receptor 2 serves an early and essential role in resistance to Mycobacterium tuberculosis

Although the protective cellular immune response to Mycobacterium tuberculosis requires recruitment of macrophages and T lymphocytes to the site of infection, the signals that regulate this trafficking have not been defined. We investigated the role of C-C chemokine receptor 2 (CCR2)-dependent cell recruitment in the protective response to M. tuberculosis. CCR2(-/-) mice died early after infection and had 100-fold more bacteria in their lungs than did CCR2(+/+) mice. CCR2(-/-) mice exhibited an early defect in macrophage recruitment to the lung and a later defect in recruitment of dendritic cells and T cells to the lung. CCR2(-/-) mice also had fewer macrophages and dendritic cells recruited to the mediastinal lymph node (MLN) after infection. T cell migration through the MLN was similar in CCR2(-/-) and CCR2(+/+) mice. However, T cell priming was delayed in the MLNs of the CCR2(-/-) mice, and fewer CD4(+) and CD8(+) T cells primed to produce IFN-gamma accumulated in the lungs of the CCR2(-/-) mice. These data demonstrate that cellular responses mediated by activation of CCR2 are essential in the initial immune response and control of infection with M. tuberculosis.

Rho-kinase mediates angiotensin II-induced monocyte chemoattractant protein-1 expression in rat vascular smooth muscle cells

Recently, it was shown that Rho-kinase plays an important role in blood pressure regulation. However, it is not known whether Rho-kinase is involved in atherogenesis. Monocyte chemoattractant protein-1 (MCP-1) is an important chemokine that regulates monocyte recruitment and atherogenesis. Therefore, we examined the role of Rho and Rho-kinase in the angiotensin (Ang) II-induced expression of MCP-1. Ang II dose- and time-dependently enhanced the expression of MCP-1 mRNA and the protein production in vascular smooth muscle cells. CV11974, an Ang II type 1 receptor (AT(1)-R) specific antagonist inhibited the enhancement of MCP-1 expression by Ang II, suggesting that the effect of Ang II is mediated by the AT(1)-R. Botulinum C3 exotoxin, a specific inhibitor of Rho, suppressed Ang II-induced MCP-1 production. To examine the role of Rho-kinase in Ang II-induced MCP-1 expression, we used adenovirus-mediated overexpression of the dominant negative mutant of Rho-kinase (AdDNRhoK) or Y-27632, a specific inhibitor of Rho-kinase. Both AdDNRhoK and Y-27632 strongly inhibited Ang II-induced MCP-1 expression. Although inhibition of extracellular signal-regulated protein kinase (ERK) by PD 098,059 also inhibited Ang II-induced MCP-1 expression, Y-27632 did not affect Ang II-induced activation of ERK. These results indicate that Rho-kinase plays a critical role in Ang II-induced MCP-1 production independent of ERK. The Rho-Rho-kinase pathway may be a novel target for the inhibition of Ang II signaling and the treatment of atherosclerosis.

Chemokines and their receptors in the central nervous system

Chemokines are a family of proteins associated with the trafficking of leukocytes in physiological immune surveillance and inflammatory cell recruitment in host defence. They are classified into four classes based on the positions of key cystiene residues: C, CC, CXC, and CX3C. Chemokines act through both specific and shared receptors that all belong to the superfamily of G-protein-coupled receptors. Besides their well-established role in the immune system, several recent reports have demonstrated that these proteins also play a role in the central nervous system (CNS). In the CNS, chemokines are constitutively expressed by microglial cells, astrocytes, and neurons, and their expression can be increased after induction with inflammatory mediators. Constitutive expression of chemokines and chemokine receptors has been observed in both developing and adult brains, and the role played by these proteins in the normal brain is the object of intense study by many research groups. Chemokines are involved in brain development and in the maintenance of normal brain homeostasis; these proteins play a role in the migration, differentiation, and proliferation of glial and neuronal cells. The chemokine stromal cell-derived factor 1 and its receptor, CXCR4, are essential for life during development, and this ligand-receptor pair has been shown to have a fundamental role in neuron migration during cerebellar formation. Chemokine and chemokine receptor expression can be increased by inflammatory mediators, and this has in turn been associated with several acute and chronic inflammatory conditions. In the CNS, chemokines play an essential role in neuroinflammation as mediators of leukocyte infiltration. Their overexpression has been implicated in different neurological disorders, such as multiple sclerosis, trauma, stroke, Alzheimer's disease, tumor progression, and acquired immunodeficiency syndrome-associated dementia. An emerging area of interest for chemokine action is represented by the communication between the neuroendocrine and the immune system. Chemokines have hormone-like actions, specifically regulating the key host physiopathological responses of fever and appetite. It is now evident that chemokines and their receptors represent a plurifunctional family of proteins whose actions on the CNS are not restricted to neuroinflammation. These molecules constitute crucial regulators of cellular communication in physiological and developmental processes.

Role of monocyte chemoattractant protein-1 in Propionibacterium acnes-induced pulmonary granulomatosis

The inflammatory process in granulomatous disorders such as sarcoidosis is mainly the consequence of delayed hypersensitivity induced by causative antigens. Propionibacterial DNA was isolated recently by PCR from human sarcoidosis tissue. Hence, we developed a model using sensitized rabbits for T cell-mediated pulmonary granulomatosis induced by Propionibacterium acnes (P. acnes) and investigated the role of monocyte chemoattractant protein-1 (MCP-1) in the pathogenesis of the granuloma formation in vivo. Intravenous injection of P. acnes into sensitized rabbits induced massive pulmonary granulomas on day 3. Maximum levels of MCP-1 in sera and bronchoalveolar lavage fluid (BALF) were detected on day 1 and preceded recruitment of monocyte/macrophages and T cells. In BALF, monocyte chemotaxis peaked 1 day after P. acnes challenge, and T cell chemotaxis peaked 3 days after P. acnes challenge. Anti-MCP-1 IgG inhibited monocyte chemotaxis by 80.2% and T cell chemotaxis by 35.7%. Phenotypic analysis of migrating T cells revealed that activated and memory T cells (CD26(+)/CD45RO(+)) but not naive cells were preferentially attracted to BALF. Administration of MCP-1 antiserum in vivo inhibited the development of granulomas in both size 59.9% reduction and number 28.6% reduction, the number of infiltrating leukocytes in BALF, and the expression of adhesion molecules on leukocytes in peripheral blood and BALF. Our data indicate that MCP-1 plays important roles in granuloma formation by attracting and activating specific types of cells in this model. Furthermore, results suggest that the rabbit model resembles human angiocentric granulomatosis and would be useful for investigating the immunopathogenesis of human pulmonary granulomatosis.

Involvement of chemokine receptor 2 and its ligand, monocyte chemoattractant protein-1, in the development of atherosclerosis: lessons from knockout mice

Blood monocytes are the precursors of the lipid-laden foam cells that are the hallmark of early atherosclerotic lesions, but the signals that initiate their recruitment to the vessel wall are poorly understood. Here, we review in vivo studies in genetically altered mice that support the notion that monocyte chemoattractant protein-1 (a member of the chemokine family of chemotactic cytokines) and chemokine receptor 2 (its cognate receptor) play important roles in this recruitment. An unexpected finding in chemokine receptor 2-knockout mice was the diminished production of interferon-gamma, which is a potent macrophage activator. The basis of this cytokine defect is not yet clear, but suggests that chemokines may influence atherosclerotic lesion development at several levels. Understanding the roles of chemokines and cytokines in atherogenesis may provide a basis for the development of future therapeutic agents that are aimed at interrupting monocyte recruitment and activation.

Neuronal MCP-1 expression in response to remote nerve injury

Direct injury of the brain is followed by inflammatory responses regulated by cytokines and chemoattractants secreted from resident glia and invading cells of the peripheral immune system. In contrast, after remote lesion of the central nervous system, exemplified here by peripheral transection or crush of the facial and hypoglossal nerve, the locally observed inflammatory activation is most likely triggered by the damaged cells themselves, that is, the injured neurons. The authors investigated the expression of the chemoattractants monocyte chemoattractant protein MCP-1, regulation on activation normal T-cell expressed and secreted (RANTES), and interferon-gamma inducible protein IP10 after peripheral nerve lesion of the facial and hypoglossal nuclei. In situ hybridization and immunohistochemistry revealed an induction of neuronal MCP-1 expression within 6 hours postoperation, reaching a peak at 3 days and remaining up-regulated for up to 6 weeks. MCP-1 expression was almost exclusively confined to neurons but was also present on a few scattered glial cells. The authors found no alterations in the level of expression and cellular distribution of RANTES or IP10, which were both confined to neurons. Protein expression of the MCP-1 receptor CCR2 did not change. MCP-1, expressed by astrocytes and activated microglia, has been shown to be crucial for monocytic, or T-cell chemoattraction, or both. Accordingly, expression of MCP-1 by neurons and its corresponding receptor in microglia suggests that this chemokine is involved in neuron and microglia interaction.

Hypoxia induces expression of the chemokines monocyte chemoattractant protein-1 (MCP-1) and IL-8 in human dermal fibroblasts

Hypoxia is an important factor in the pathophysiology of vascular and inflammatory diseases. Leucocyte infiltration, as a consequence of adhesion molecule up-regulation and chemokine release, is a prominent feature of these diseases. The objective of our study was to investigate the potential role of resident fibroblasts in hypoxia-induced chemotactic responses. We show that MCP-1 and IL-8 mRNA are specifically induced by hypoxia in dermal fibroblasts. This response is paralleled by increased NF-kappaB p65/p50 binding activity, and it is inhibited by pretreatment with N-acetyl-L-cysteine. MCP-1 secreted by fibroblasts is chemotactic for monocytic cells and this activity is significantly increased by hypoxia. Chemotactic index correlates with MCP-1 protein levels and is significantly decreased by neutralizing anti-MCP-1 MoAb. These findings demonstrate the ability of resident fibroblasts to mediate chemotaxis of leucocytes through the release of chemokines in response to hypoxia. Our data point to MCP-1 as an important component in this response, and therefore it may be a potential target in inflammatory responses associated with hypoxia.

Modulation of macrophage recruitment into wounds by monocyte chemoattractant protein-1

Previous studies suggest that normal wound repair requires the regulated production of monocyte and macrophage chemoattractants. The current study examines the role of monocyte chemoattractant protein-1 (MCP-1) in coordinating monocyte recruitment into sites of injury. MCP-1 protein was detected in both incisional and excisional murine wounds, with a peak concentration occurring slightly before maximum macrophage infiltration. Compared to wounds treated with control antibody, wounds treated with a neutralizing monoclonal anti-MCP-1 antibody contained significantly fewer macrophages (8.2 +/- 0.9 vs. 14 +/- 1.7 macrophages per high power field, p < 0.05). Conversely, the addition of recombinant MCP-1 to wounds resulted in a substantial increase in the number of macrophages (107% to 124% increase over untreated wounds, p < 0.01). Because macrophages promote wound healing, the effect of recombinant MCP-1 on the wound healing process was examined. Incisional wounds (n = 12) were either left untreated or treated with vehicle alone, 5 ng recombinant MCP-1 in vehicle, or 50 ng recombinant MCP-1 in vehicle. Wound disruption strength was determined on days 7, 14, 21, and 28 for each group. Wounds treated with MCP-1 exhibited a slight increase in wound disruption strength at nearly all time points but this increase did not reach statistical significance. Addition of 100 ng of MCP-1 to excisional wounds did not have any significant effect on wound reepithelialization. Taken together, the results show that MCP-1 is produced within wounds at physiologic concentrations, and is an important positive regulator of macrophage recruitment into sites of injury. Addition of exogenous MCP-1 to wounds of normal mice yields only modest enhancement of the repair process.

A mechanism for the impaired IFN-gamma production in C-C chemokine receptor 2 (CCR2) knockout mice: role of CCR2 in linking the innate and adaptive immune responses

We have recently shown that mice with a targeted disruption of CCR2, the receptor for monocyte chemoattractant protein-1, have markedly impaired recruitment of macrophages to sites of inflammation. An unexpected finding in the CCR2(-/-) mice was a dramatic decrease in the production of IFN-gamma after challenge with purified protein derivative of Mycobacterium bovis. In this study, we have investigated the mechanism of this cytokine production defect. In vitro, direct activation of splenocytes with CD3/CD28 Abs failed to reveal any differences in IFN-gamma production between CCR2(+/+) and CCR2(-/-) mice. However, after immunization, the number of Ag-specific, IFN-gamma-producing cells in the draining lymph nodes was decreased by 70% in the CCR2(-/-) mice, suggesting an in vivo trafficking defect. Direct measurement of cell trafficking with fluorescently labeled CFA revealed a marked decrease in the number of monocytes/macrophages migrating to the site of immunization and to the draining lymph nodes in the CCR2(-/-) mice. The data suggest that impaired trafficking of APCs in the CCR2(-/-) mice contributes to the defect in IFN-gamma production. These data support the idea that CCR2-positive monocytes/macrophages are critical in linking the innate and adaptive immune responses.

Functional differences between monocyte chemotactic protein-1 receptor A and monocyte chemotactic protein-1 receptor B expressed in a Jurkat T cell

The monocyte chemotactic protein-1 (MCP-1) receptor (MCP-1R) is expressed on monocytes, a subpopulation of memory T lymphocytes, and basophils. Two alternatively spliced forms of MCP-1R, CCR2A and CCR2B, exist and differ only in their carboxyl-terminal tails. To determine whether CCR2A and CCR2B receptors function similarly, Jurkat T cells were stably transfected with plasmids encoding the human CCR2A or CCR2B gene. Nanomolar concentrations of MCP-1 induced chemotaxis in the CCR2B transfectants that express high, intermediate, and low levels of MCP-1R. Peak chemotactic activity was shifted to the right as receptor number decreased. Five-fold more MCP-1 was required to initiate chemotaxis of the CCR2A low transfectant, but the peak of chemotaxis was similar for the CCR2A and CCR2B transfectants expressing similar numbers of receptors. MCP-1-induced chemotaxis was sensitive to pertussis toxin, implying that both CCR2A and CCR2B are G(i)alpha protein coupled. MCP-1 induced a transient Ca(2+) flux in the CCR2B transfectant that was partially sensitive to pertussis toxin. In contrast, MCP-1 did not induce Ca(2+) flux in the CCR2A transfectant. Since MCP-1 can stimulate chemotaxis of the CCR2A transfectant without inducing Ca(2+) mobilization, Ca(2+) flux may not be required for MCP-1-induced chemotaxis in the Jurkat transfectants. These results indicate that functional differences exist between the CCR2A and CCR2B transfectants that can be attributed solely to differences in the carboxyl-terminal tail.

Oxidized LDL reduces monocyte CCR2 expression through pathways involving peroxisome proliferator-activated receptor gamma

The CCR2-mediated recruitment of monocytes into the vessel wall plays an important role in all stages of atherosclerosis. In recent studies, we have shown that lipoproteins can modulate CCR2 expression and have identified native LDL as a positive regulator. In contrast, oxidized LDL (OxLDL), which is mainly formed in the aortic intima, reduces CCR2 expression, promotes monocyte retention, and may cause pathological accumulation of monocytes in the vessel wall. We now provide evidence that OxLDL reduces monocyte CCR2 expression by activating intracellular signaling pathways that may involve peroxisome proliferator-activated receptor gamma (PPARgamma). Receptor-mediated uptake of the lipoprotein particle was required and allows for delivery of the exogenous ligand to the nuclear receptor. The suppression of CCR2 expression by OxLDL was mediated by lipid components of OxLDL, such as the oxidized linoleic acid metabolites 9-HODE and 13-HODE, known activators of PPARgamma. Modified apoB had no such effect. Consistent with a participation of the PPARgamma signaling pathway, BRL49653 reduced CCR2 expression in freshly isolated human monocytes ex vivo and in circulating mouse monocytes in vivo. These results implicate PPARgamma in the inhibition of CCR2 gene expression by oxidized lipids, which may help retain monocytes at sites of inflammation, such as the atherosclerotic lesion.

Human endothelial cells express CCR2 and respond to MCP-1: direct role of MCP-1 in angiogenesis and tumor progression

Although several CXC chemokines have been shown to induce angiogenesis and play roles in tumor growth, to date, no member of the CC chemokine family has been reported to play a direct role in angiogenesis. Here we report that the CC chemokine, monocyte chemotactic protein 1 (MCP-1), induced chemotaxis of human endothelial cells at nanomolar concentrations. This chemotactic response was inhibited by a monoclonal antibody to MCP-1. MCP-1 also induced the formation of blood vessels in vivo as assessed by the chick chorioallantoic membrane and the matrigel plug assays. As expected, the angiogenic response induced by MCP-1 was accompanied by an inflammatory response. With the use of a rat aortic sprouting assay in the absence of leukocytic infiltrates, we ruled out the possibility that the angiogenic effect of MCP-1 depended on leukocyte products. Moreover, the direct effect of MCP-1 on angiogenesis was consistent with the expression of CCR2, the receptor for MCP-1, on endothelial cells. Assessment of supernatant from a human breast carcinoma cell line demonstrated the production of MCP-1. Treatment of immunodeficient mice bearing human breast carcinoma cells with a neutralizing antibody to MCP-1 resulted in significant increases in survival and inhibition of the growth of lung micrometastases. Taken together, our data indicate that MCP-1 can act as a direct mediator of angiogenesis. As a chemokine that is abundantly produced by some tumors, it can also directly contribute to tumor progression. Therefore, therapy employing antagonists of MCP-1 in combination with other inhibitors of angiogenesis may achieve more comprehensive inhibition of tumor growth.