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PubMed2006

Regulation of FAS ligand expression by chemokine ligand 2 in human endometrial cells.

Human endometrium is a dynamic tissue under the influence of numerous hormones, growth factors, and cytokines interacting to maintain a balance of cellular growth, differentiation, and apoptosis. We have previously demonstrated that several factors including interleukin-8, extracellular matrix, and steroid hormones modulate FASLG, one of the apoptotic molecules, in human endometrium. Chemokine ligand 2 (CCL2), a monocyte chemoattractant and activating factor, is a cytokine involved in endometrial function. CCL2 is elevated in the peritoneal fluid of women with endometriosis. We hypothesize that increased levels of CCL2 in the endometriotic environment may upregulate FASLG expression in human endometrial stromal cells and induce a local immunotolerance in endometriosis. To test our hypothesis, we studied the in vitro regulation of FASLG expression and apoptosis by CCL2 in endometrial stromal cells. Western blot analysis revealed that CCL2 upregulated FASLG protein expression in cultured endometrial stromal cells. Based on semiquantitative RT-PCR analysis, CCL2 did not alter either FAS or FASLG mRNA expression in endometrial stromal cells. Immunocytochemistry results from the same cells treated with CCL2 demonstrated upregulation of FASLG protein expression. CCL2 did not change rate of apoptosis in endometrial stromal cells as evaluated by TUNEL assay. However, an increased apoptotic rate was detected in Jurkat (T lymphocytes) cells cocultured with endometrial stromal cells previously treated with CCL2. We speculate that increased FASLG expression by CCL2 may induce apoptosis of T lymphocytes and thus produce an immunotolerant environment for the development of ectopic implants.

Adult↗

PubMed2005

Role for IL-4 nonproducing NKT cells in CC-chemokine ligand 2-induced Th2 cell generation.

NKT cells from C57Bl/6 mice are known to be the initial cellular source of IL-4 that acts as a trigger for Th2 cell differentiation. CC-chemokine ligand 2 (CCL2) has been described as an initial stimulator of IL-4 production by these cells; however, IL-4 was not produced by NKT cells from BALB/c mice even when Th2 cell responses were established in these mice. In this study, we found a new pathway for CCL2-associated Th2 cell generation in BALB/c mice. Splenic T cells from BALB/c mice produced IL-4 in response to CCL2 stimulation. However, IL-4 production was not seen in cultures of splenic T cells from CD1-/- mice (BALB/c origin), whereas, in the presence of CCL2, splenic T cells from CD1-/- mice produced IL-4 when NKT cells from wild-type mice were added. CCL2 induced IL-4 in cultures of NKT cells cocultured with naive T cells, but IL-4 was not produced by these cells cultured separately with CCL2. Interestingly, IL-4 was produced by naive T cells cocultured with NKT cells that were previously treated with CCL2 (CCL2-NKT cells). In addition, IL-4 was produced by naive T cells supplemented with a culture supernatant of CCL2-NKT cells. These results indicate that, through the production of a soluble factor(s) other than IL-4, NKT cells play a role in the CCL2-associated generation of Th2 cells.

Animals↗

PubMed2002

The role of CC chemokine receptor 2 in alveolar monocyte and neutrophil immigration in intact mice.

The CC chemokine ligand 2 (CCL2) (JE, monocyte chemotactic protein-1 [MCP-1]) and its CC chemokine receptor 2 (CCR2) are critical regulators of monocyte/macrophage trafficking. Recently, we demonstrated that application of exogenous CCL2 in the lungs of mice induced monocyte accumulation in the airspace, whereas combined bronchoalveolar instillation of CCL2 and Escherichia coli endotoxin provoked both enhanced monocyte accumulation and extensive neutrophil influx associated with loss of pulmonary endothelial/epithelial barrier function. In this study, we investigated the role of the CCL2 receptor CCR2 in alveolar leukocyte traffic. In CCR2 knockout mice or wild-type mice treated with the anti-CCR2-blocking monoclonal antibody MC21, monocyte accumulation in response to alveolar CCL2 or CCL2 plus endotoxin was inhibited by more than 90%. Unexpectedly, alveolar neutrophil accumulation in the CCL2/lipopolysaccharide (LPS) model was also drastically reduced by both approaches of CCR2 function interference. When wild-type mice treated with anti-Gr-1 monoclonal antibody to deplete neutrophils selectively or treated with antileukinate, a CXC receptor inhibitor, were challenged with alveolar CCL2 plus LPS, alveolar monocyte accumulation was markedly decreased. Wild-type mice treated with MC21 to block CCR2 function or with anti-Gr-1 to deplete neutrophils did not exhibit the vascular leakage that typically accompanies inflammation triggered by CCL2 and LPS in wild-type mice. These findings confirm a central role for CCR2 in the process of alveolar monocyte recruitment in response to CCL2 alone and combined CCL2 plus LPS and reveal a previously unobserved interdependence between monocyte and neutrophil trafficking that has important implications for the concomitant increase in vascular permeability.

Acute Disease↗

PubMed2005

C-C chemokine ligand 2 gene expression in nasal polyp fibroblasts: possible implication in the pathogenesis of nasal polyposis.

OBJECTIVES: Recruitment of macrophages is essential to the pathogenesis of nasal polyps (NP), since this disease is inflammation-related. In this study, the effects of tumor necrosis factor alpha (TNF-alpha) on the expression of C-C chemokine ligand 2 (CCL2) in fibroblasts derived from nasal polyps (NPFs) were investigated. The roles of cyclooxygenase (COX) 2 and prostaglandins in the mediation of TNF-alpha-stimulated CCL2 gene expression were also investigated. METHODS: Northern blot analysis was used to study the expression of CCL2 and c-Fos in cultured NPFs. An electrophoretic mobility shift assay was used to explore the interactions between activator protein 1 (AP- 1) and DNA. Immunohistochemistry was used to explore the in vivo expressions of COX-2, CCL2, and CD68 in NPs. RESULTS: The Northern blot analysis showed that TNF-alpha stimulated the expression of CCL2 and COX-2 genes, and the synthesis of CCL2 messenger RNA was COX-2-dependent. A transient elevation of c-Fos and c-Jun messenger RNAs was induced by TNF-alpha, whereas COX-2 inhibitors NS-398 and meloxicam abolished the up-regulation of c-Fos. The electrophoretic mobility shift assay revealed that TNF-alpha triggered AP-1 and DNA binding and again, NS-398 and meloxicam inhibited this reaction via reducing c-Fos synthesis. Curcumin (AP-1 inhibitor) markedly suppressed the TNF-alpha-induced CCL2 expression. The immunohistochemical staining of NP surgical specimens also revealed an intimate alignment between CCL2-positive fibroblasts and CD-68-positive macrophages. CONCLUSIONS: These data suggest that NPFs may contribute to NP development by synthesizing CCL2 to promote macrophage recruitment. Furthermore, COX-2 facilitates CCL2 transcription in NPFs via a c-Fos and AP-1 signaling pathway.

Cells, Cultured↗

PubMed2004

Role of donor-derived monocyte chemoattractant protein-1 in murine islet transplantation.

Monocyte chemoattractant protein-1 (CCL2/MCP-1) is a proinflammatory chemokine produced by several cell types, including pancreatic islets. High levels of donor-derived CCL2 have been associated with poor islet allograft outcome in patients with type 1 diabetes; however, the causal relationship is unknown. The constitutive and inducible expression of chemokines and their receptors by pancreatic islets in vitro were investigated, specifically the role of donor-derived CCL2 in marginal mass murine islet transplantation. The results showed that inflammatory cytokine stimulation of islets induced de novo expression of CCL2, CCL5/RANTES, CXCL9/MIG, and CXCL10/IP-10 and increased expression of CXCL2/macrophage-inflammatory protein-2. CCL2 mRNA and protein were highly expressed within 2 d in cultures. Transplantation of islets with high levels of CCL2 into syngeneic recipients led to a significantly greater influx of CCR2(+) cells and higher expression of monocyte/macrophage-associated inflammatory cytokines compared with low CCL2-donor islets. The level of pretransplantation CCL2 inversely correlated (P < 0.0001) with isograft function. In contrast, in CCR2-/- recipients, this correlation was not present. A direct toxic effect of CCL2 on islets was excluded by assessing cell viability and insulin release in vitro. In conclusion, CCL2 secreted by islets plays an important role in the immediate islet graft function. Strategies to decrease islet-derived CCL2 release may increase the success of islet transplantation.

Animals↗

PubMed2002

Differential roles of CC chemokine ligand 2/monocyte chemotactic protein-1 and CCR2 in the development of T1 immunity.

CCR2 and its major ligand, chemokine ligand 2 (CCL2)/monocyte chemotactic protein-1, have been found to influence T1/T2 immune response polarization. Our objective was to directly compare the roles of CCR2 and CCL2 in T1/T2 immune response polarization using a model of pulmonary Cryptococcus neoformans infection. Either deletion of CCR2 or treatment of wild-type mice with CCL2 neutralizing Ab produced significant and comparable reductions in macrophage and T cell recruitment into the lungs following infection. Both CCL2 neutralization and CCR2 deficiency resulted in significantly diminished IFN-gamma production, and increased IL-4 and IL-5 production by lung leukocytes (T1 to T2 switch), but only CCR2 deficiency promoted pulmonary eotaxin production and eosinophilia. In the lung-associated lymph nodes (LALN), CCL2-neutralized mice developed Ag-specific IFN-gamma-producing cells, while CCR2 knockout mice did not. LALN from CCR2 knockout mice also had fewer MHCII(+)CD11c(+) and MHCII(+)CD11b(+) cells, and produced significantly less IL-12p70 and TNF-alpha when stimulated with heat-killed yeast than LALN from wild-type or CCL2-neutralized mice, consistent with a defect in APC trafficking in CCR2 knockout mice. Neutralization of CCL2 in CCR2 knockout mice did not alter immune response development, demonstrating that the high levels of CCL2 in these mice did not play a role in T2 polarization. Therefore, CCR2 (but not CCL2) is required for afferent T1 development in the lymph nodes. In the absence of CCL2, T1 cells polarize in the LALN, but do not traffic from the lymph nodes to the lungs, resulting in a pulmonary T2 response.

Animals↗

PubMed2005

MCP-1/CCL2 protects cardiac myocytes from hypoxia-induced apoptosis by a G(alphai)-independent pathway.

Chemokines, in addition to their chemotactic properties, act upon resident cells within a tissue and mediate other cellular functions. In a previous study, we demonstrated that CCL2 protects cultured mouse neonatal cardiac myocytes from hypoxia-induced cell death. Leukocyte chemotaxis has been shown to contribute to ischemic injury. While the chemoattractant properties of CCL2 have been established, the protective effects of this chemokine suggest a novel role for CCL2 in myocardial ischemia/reperfusion injury. The present study examined the cellular signaling pathways that promote this protection. Treatment of cardiac myocyte cultures with CCL2 protected them from hypoxia-induced apoptosis. This protection was not mediated through the activation of G(alphai) signaling that mediates monocyte chemotaxis. Inhibition of the ERK1/2 signaling pathway abrogated CCL2 protection. Caspase 3 activation and JNK/SAPK phosphorylation were decreased in hypoxic myocytes co-treated with CCL2 as compared to hypoxia only-treated cultures. Expression of the Bcl-2 family proteins, Bcl-xL and Bag-1, was increased in CCL2-treated myocytes subjected to hypoxia. There was also downregulation of Bax protein levels as a result of CCL2 co-treatment. These data suggest that CCL2 cytoprotection and chemotaxis may occur through distinct signaling mechanisms.

Animals↗

PubMed2006

Sequence variation in the CC-chemokine ligand 2 promoter of pigtailed macaques is not associated with the incidence or severity of neuropathology in a simian immunodeficiency virus model of human immunodeficiency virus central nervous system disease.

Increased expression of CC-chemokine ligand 2 (CCL2) in the cerebrospinal fluid (CSF) and brain is consistently observed in human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) central nervous system (CNS) disease. The molecular basis for the correlation between increased expression of CCL2 and HIV neuropathogenesis has been linked to a polymorphism at -2578 in the promoter of human CCL2, which was reported to influence the rate of progression to acquired immunodeficiency syndrome (AIDS) and the predisposition of HIV-infected individuals to develop HIV-associated dementia. However, because the rate of neurological deterioration essentially parallels the progression of immunosuppression, it is inherently difficult to uncouple the influence of this polymorphism on increased progression to AIDS from increased propensity to develop CNS complications. To further investigate the correlation between CCL2 and HIV/SIV CNS disease, the authors sequenced the CCL2 promoter of 29 pigtailed macaques examined in their accelerated and consistent SIV model in which all infected macaques develop AIDS but only 69% developed moderate/severe CNS lesions. Sequence analysis identified 39 sites of nucleotide variation in the pigtailed macaque CCL2 promoter/enhancer regions, with the resulting consensus sequence aligning with 94.7% homology to the human CCL2 promoter. After genetic analyses, no variation was found to correlate with the incidence or severity of CNS lesions or with levels of CCL2 in plasma or CSF. These findings suggest that the determinants of neuropathogenesis in this SIV model are distinct from variation in these regions of the CCL2 promoter.

Acquired Immunodeficiency Syndrome↗

PubMed2006

The role of CCL12 in the recruitment of fibrocytes and lung fibrosis.

We have previously shown that mice that are genetically deficient in the CCR2 gene (CCR2-/- mice) are protected from fluorescein isothiocyanate (FITC)-induced lung fibrosis. Protection from fibrosis correlated with impaired recruitment of fibrocytes (bone marrow-derived cells, which share both leukocyte and mesenchymal markers). There are three ligands for CCR2 in the mouse: CCL2, CCL7, and CCL12. CCL2 and CCL12 are both elevated in the lung after FITC injury, but with different kinetics. CCL2 is maximal at Day 1 and absent by Day 7 after FITC. In contrast, CCL12 peaks at Day 3, but remains elevated through Day 21 after FITC. We now demonstrate that while CCR2-/- mice are protected from FITC-induced fibrosis, CCL2-/- mice are not. CCL2-/- mice are able to recruit fibrocytes to FITC-injured airspaces, unlike CCR2-/- mice. Adoptive transfer of CCR2-expressing fibrocytes augments FITC-induced fibrosis in both wild-type and CCR2-/- mice, suggesting that these cells play a pathogenic role in the disease process. Both CCL2 and CCL12 are chemotactic for fibrocytes. However, neutralization of CCL12 in wild-type mice significantly protects from FITC-induced fibrosis, whereas neutralization of CCL2 was less effective. Thus, CCL12 is likely the CCR2 ligand responsible for driving fibroproliferation in the mouse. As murine CCL12 is homologous to human CCL2, we suggest that the pathobiology of murine CCL12 in fibroproliferation may correlate to human CCL2 biology.

Adoptive Transfer↗

PubMed2006

Astrocyte differentiation selectively upregulates CCL2/monocyte chemoattractant protein-1 in cultured human brain-derived progenitor cells.

Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play roles in both neurodevelopment and neuropathology. Increased brain levels of monocyte chemoattractant protein-1 (MCP-1), also known as CCL2, are found in patients with human immunodeficiency virus type 1 (HIV-1)-associated dementia and other acute and chronic neurologic diseases. Although the function of CCL2 in the brain is unclear, it is believed that upregulation of this chemokine during neuropathologic or neuroinflammatory conditions leads to recruitment of activated monocytes into the brain, where they differentiate into macrophages producing neurotoxic and inflammatory molecules. We recently showed that human fetal brain-derived progenitor cells are susceptible to HIV-1 and JC virus infection, and that differentiation toward an astrocyte phenotype increased virus production from these cells. In the current study, we found that in the absence of infection, progenitors produced moderate levels of CCL2 (5.6 ng per million cells). Astrocyte differentiation over 3 weeks increased CCL2 protein levels 30-fold in a biphasic manner, whereas neuronal differentiation decreased production 20-fold. Electromobility shift assays (EMSAs) demonstrated increased nuclear NF-kappaB levels within 2 h of initiating astrocyte differentiation, and inhibitors of NF-kappaB activation partially blocked the CCL2 increase in differentiating astrocytes. Transfection of progenitors with mutated CCL2 promoter/CAT reporter constructs showed that the distal promoter region, containing NF-kappaB and NF-I binding sites, is important for differentiation-induced CCL2 upregulation. Together these results suggest that the transcription factor NF-kappaB, and possibly NF-I, contribute to the upregulation of CCL2 chemokine production during the differentiation of human progenitor cells toward an astrocyte phenotype.

AIDS Dementia Complex↗

PubMed2006

CC chemokine receptor 2 is protective against noise-induced hair cell death: studies in CX3CR1(+/GFP) mice.

Acoustic trauma was recently shown to induce an inflammatory response in the ear characterized by rapid entry of macrophages in the spiral ligament. The current study seeks to elucidate the mechanisms involved in summoning macrophages to the cochlear lateral wall and the role macrophages play in noise-induced injury or repair. CCL2 and its primary receptor, CCR2, are the most widely validated effectors of monocyte chemotaxis in vivo. CCL2-/- and CCR2-/- mice have been used extensively in studies of monocyte activation in neuronal injury. However, the function of CCL2 and CCR2 in the cochlea has not been studied. The present study examines the role of CCL2 and CCR2 in acoustic injury. CCL2-/- and CCR2-/- mice on a CX3CR1(+/GFP) background were exposed to octave band noise (8-16 kHz) for 2 h to determine the effect of CCL2 and CCR2 on monocyte migration into the cochlea, threshold shift, and cell survival. We found that threshold shift was unchanged in the two knockout mouse strains when compared to the background strain (CX3CR1(+/GFP)). Surprisingly, we found that monocyte migration was also unchanged, despite the absence of CCL2 or CCR2. However, there was a dramatic increase in noise-induced hair cell death in the CCR2-/- strain. This observation suggests that CCR2, independent of CCL2, plays a protective role in the cochlea after noise, and neither ligand nor receptor is necessary for monocyte migration. Possible mechanisms of neuroprotection by CCR2 are discussed.

Animals↗

PubMed2005

Chronic expression of monocyte chemoattractant protein-1 in the central nervous system causes delayed encephalopathy and impaired microglial function in mice.

Increased central nervous system (CNS) levels of monocyte chemoattractant protein 1 [CC chemokine ligand 2 (CCL2) in the systematic nomenclature] have been reported in chronic neurological diseases such as human immunodeficiency virus type 1-associated dementia, amyotrophic lateral sclerosis, and multiple sclerosis. However, a pathogenic role for CCL2 has not been confirmed, and there is no established model for the effects of chronic CCL2 expression on resident and recruited CNS cells. We report that aged (>6 months) transgenic (tg) mice expressing CCL2 under the control of the human glial fibrillary acidic protein promoter (huGFAP-CCL2hi tg+ mice) manifested encephalopathy with mild perivascular leukocyte infiltration, impaired blood brain barrier function, and increased CD45-immunoreactive microglia, which had morphologic features of activation. huGFAP-CCL2hi tg+ mice lacking CC chemokine receptor 2 (CCR2) were normal, showing that chemokine action via CCR2 was required. Studies of cortical slice preparations using video confocal microscopy showed that microglia in the CNS of huGFAP-CCL2hi tg+ mice were defective in expressing amoeboid morphology. Treatment with mutant CCL2 peptides, a receptor antagonist and an obligate monomer, also suppressed morphological transformation in this assay, indicating a critical role for CCL2 in microglial activation and suggesting that chronic CCL2 exposure desensitized CCR2 on microglia, which in the CNS of huGFAP-CCL2hi tg+ mice, did not up-regulate cell-surface expression of major histocompatibility complex class II, CD11b, CD11c, or CD40, in contrast to recruited perivascular macrophages that expressed enhanced levels of these markers. These results indicate that huGFAP-CCL2hi tg+ mice provide a useful model to study how chronic CNS expression of CCL2 alters microglial function and CNS physiology.

Animals↗

PubMed2005

CCR2 and CXCR3 agonistic chemokines are differently expressed and regulated in human alveolar epithelial cells type II.

The attraction of leukocytes from circulation to inflamed lungs depends on the activation of both the leukocytes and the resident cells within the lung. In this study we determined gene expression and secretion patterns for monocyte chemoattractant protein-1 (MCP-1/CCL2) and T-cell specific CXCR3 agonistic chemokines (Mig/CXCL9, IP-10/CXCL10, and I-TAC/CXCL11) in TNF-alpha-, IFN-gamma-, and IL-1beta-stimulated human alveolar epithelial cells type II (AEC-II). AEC-II constitutively expressed high level of CCL2 mRNA in vitro and in situ , and released CCL2 protein in vitro . Treatment of AEC-II with proinflammatory cytokines up-regulated both CCL2 mRNA expression and release of immunoreactive CCL2, whereas IFN-gamma had no effect on CCL2 release. In contrast, CXCR3 agonistic chemokines were not detected in freshly isolated AEC-II or in non-stimulated epithelial like cell line A549. IFN-gamma, alone or in combination with IL-1beta and TNF-alpha resulted in an increase in CXCL10, CXCL11, and CXCL9 mRNA expression and generation of CXCL10 protein by AEC-II or A549 cells. CXCL10 gene expression and secretion were induced in dose-dependent manner after cytokine-stimulation of AEC-II with an order of potency IFN-gamma > > IL-1beta > or = TNF-alpha. Additionally, we localized the CCL2 and CXCL10 mRNAs in human lung tissue explants by in situ hybridization, and demonstrated the selective effects of cytokines and dexamethasone on CCL2 and CXCL10 expression. These data suggest that the regulation of the CCL2 and CXCL10 expression exhibit significant differences in their mechanisms, and also demonstrate that the alveolar epithelium contributes to the cytokine milieu of the lung, with the ability to respond to locally generated cytokines and to produce potent mediators of the local inflammatory response.

Cells, Cultured↗

PubMed2004

The CC chemokine ligand, CCL2/MCP1, participates in macrophage fusion and foreign body giant cell formation.

The foreign body reaction (FBR) develops in response to the implantation of almost all biomaterials and can be detrimental to their function. The formation of foreign body giant cells (FBGC), which damage the surface of biomaterials, is considered a hallmark of this reaction. FBGC derive from blood-borne monocytes that enter the implantation site after surgery in response to the release of chemotactic signals. In this study, we implanted biomaterials subcutaneous (s.c.) in mice that lack the monocyte chemoattractant CC chemokine ligand 2 (CCL2) and found that biomaterials were encapsulated despite reduced FBGC formation. The latter was due to compromised macrophage fusion rather than migration. Consistent with the reduction in FBGC formation, biodegradable biomaterials sustained reduced damage in CCL2-null mice. Furthermore, blockade of CCL2 function by localized gene delivery in wild-type mice hindered FBGC formation, despite normal monocyte recruitment. The requirement for CCL2 in fusion was confirmed by the ability of both a CCL2 inhibitory peptide and an anti-CCL2 Ab to reduce FBGC formation from peripheral blood monocytes in an in vitro assay. Our findings demonstrate a previously unreported involvement of CCL2 in FBGC formation, and suggest that FBGC are not the primary determinants of capsule formation in the FBR.

Animals↗

PubMed2004

Platelet-activating factor-induced chemokine gene expression requires NF-kappaB activation and Ca2+/calcineurin signaling pathways. Inhibition by receptor phosphorylation and beta-arrestin recruitment.

Previously, we reported that platelet-activating factor (PAF) stimulates higher G protein activation and a more robust Ca2+ mobilization in RBL-2H3 cells expressing carboxyl terminus deletion, phosphorylation-deficient mutant of PAF receptor (mPAFR) when compared with the wild-type receptor (PAFR). However, PAF did not provide sufficient signal for CC chemokine receptor ligand 2 (CCL2) production in cells expressing mPAFR. Based on these findings, we hypothesized that receptor phosphorylation provides a G protein-independent signal that synergizes with Ca2+ mobilization to induce CCL2 production. Here, we show that a mutant of PAFR (D289A), which does not couple to G proteins, was resistant to agonist-induced receptor phosphorylation. Unexpectedly, we found that when this mutant was coexpressed with mPAFR, it restored NF-kappaB activation and CCL2 production. PAF caused translocation of beta-arrestin from the cytoplasm to the membrane in cells expressing PAFR but not a phosphorylation-deficient mutant in which all Ser/Thr residues were replaced with Ala (DeltaST-PAFR). Interestingly, PAF induced significantly higher NF-kappaB and nuclear factor of activated T cells (NFAT)-luciferase activity as well as CCL2 production in cells expressing DeltaST-PAFR than those expressing PAFR. Furthermore, a Ca2+/calcineurin inhibitor completely inhibited PAF-induced NFAT activation and CCL2 production but not NF-kappaB activation. These findings suggest that the carboxyl terminus of PAFR provides a G protein-independent signal for NF-kappaB activation, which synergizes with G protein-mediated Ca2+/calcineurin activation to induce CCL2 production. However, receptor phosphorylation and beta-arrestin recruitment inhibit CCL2 production by blocking both NF-kappaB activation and Ca2+/calcineurin-dependent signaling pathways.

Amino Acid Sequence↗

PubMed2004

Membrane type 1-matrix metalloproteinase is regulated by chemokines monocyte-chemoattractant protein-1/ccl2 and interleukin-8/CXCL8 in endothelial cells during angiogenesis.

We have investigated the putative role and regulation of membrane type 1-matrix metalloproteinase (MT1-MMP) in angiogenesis induced by inflammatory factors of the chemokine family. The absence of MT1-MMP from null mice or derived mouse lung endothelial cells or the blockade of its activity with inhibitory antibodies resulted in the specific decrease of in vivo and in vitro angiogenesis induced by CCL2 but not CXCL12. Similarly, CCL2- and CXCL8-induced tube formation by human endothelial cells (ECs) was highly dependent on MT1-MMP activity. CCL2 and CXCL8 significantly increased MT1-MMP surface expression, clustering, activity, and function in human ECs. Investigation of the signaling pathways involved in chemokine-induced MT1-MMP activity in ECs revealed that CCL2 and CXCL8 induced cortical actin polymerization and sustained activation of phosphatidylinositol 3-kinase (PI3K) and the small GTPase Rac. Inhibition of PI3K or actin polymerization impaired CCL2-induced MT1-MMP activity. Finally, dimerization of MT1-MMP was found to be enhanced by CCL2 in ECs in a PI3K- and actin polymerization-dependent manner. In summary, we identify MT1-MMP as a molecular target preferentially involved in angiogenesis mediated by CCL2 and CXCL8, but not CXCL12, and suggest that MT1-MMP dimerization might be an important mechanism of its regulation during angiogenesis.

Actins↗

PubMed2005

Cooperative expression of monocyte chemoattractant protein 1 within the bovine corpus luteum: evidence of immune cell-endothelial cell interactions in a coculture system.

Endothelial cells (EC) of the bovine corpus luteum (CL) are a known source of proinflammatory mediators, including monocyte chemoattractant protein 1 (CCL2) and endothelin 1 (EDN1). Here, a coculture system was devised to determine if immune cells and PGF 2alpha together affect CCL2 and EDN1 secretion by EC. Luteal EC were cultured either alone or together with peripheral blood mononuclear cells (PBMC), and treated without or with PGF 2alpha for 48 h (n = 6 experiments). Coculture of EC with PBMC increased CCL2 secretion an average of 5-fold higher compared with either cell type alone (P < 0.05). Basal secretion of EDN1 by EC was substantial (approximately 2 ng/ml), but was not affected by coculture with PBMC (P > 0.05). EC cocultured with concanavalin A-activated PBMC (ActPBMC) increased CCL2 secretion an average of 12-fold higher compared with controls (P < 0.05), but again, EDN1 secretion was unchanged (P > 0.05). Interestingly, PGF 2alpha did not alter either CCL2 or EDN1 secretion, regardless of culture conditions (P > 0.05). In a second series of experiments (n = 3 experiments), mixed luteal cells (MLC) were cultured alone or with PBMC as described above. Secretion of CCL2 and EDN1 was not affected by coculture or by PGF 2alpha (P > 0.05), but MLC produced less progesterone in the presence of ActPBMC (P < 0.05). Collectively, these results suggest that immune cells and EC can interact cooperatively to increase CCL2 secretion in the CL, but this interaction does not affect EDN1 secretion nor is it influenced by PGF 2alpha. Additionally, activated immune cells appear to produce a factor that impairs progesterone production by luteal steroidogenic cells.

Animals↗

PubMed2003

CC chemokine ligand 2 and its receptor regulate mucosal production of IL-12 and TGF-beta in high dose oral tolerance.

Oral tolerance is the result of a complex immunoregulatory strategy used by the gut and its associated lymphoid tissues to render the peripheral immune system unresponsive to nonpathogenic proteins, such as food or commensal bacteria. The mechanism of oral tolerance induction and maintenance is not well understood. We have previously shown that the chemokine, CC chemokine ligand 2 (CCL2), is important for the induction and maintenance of oral tolerance. To address the role CCL2 plays in oral tolerance, we used both CCL2(-/-) and CCR2(-/-) mice. Cells from the spleen, mesenteric lymph nodes, and peripheral lymph nodes of CCL2(-/-) and CCR2(-/-) mice fed high doses of OVA showed robust proliferative responses compared with cells from Ag-fed wild-type mice. CCL2(-/-) and CCR2(-/-) mice also produced high amounts of Th1 cytokines such as IL-2 and IFN-gamma and very low amounts of IL-4 and IL-10. The ability of APCs from the gut of CCL2(-/-) and CCR2(-/-) OVA-fed mice to stimulate an indicator T cell line was evaluated. APCs from the Peyer's patch of OVA-fed knockout animals could induce a T cell response measured by an increase in proliferation and generation of IL-12 and IFN-gamma with a concomitant reduction of TGF-beta compared with wild-type controls that did not induce a Th1 response. These data indicate that CCL2 and signaling through its receptor CCR2 is critical for the induction of oral tolerance by regulating Ag presentation leading to a disruption in the balance of inflammatory and regulatory cytokines.

Administration, Oral↗