Molecular mechanism and role of endothelial monocyte chemoattractant protein-1 induction by vascular endothelial growth factor

MCP-1: chemoattractant with a role beyond immunity: a review

BACKGROUND

Monocyte Chemoattractant Protein (MCP)-1, a potent monocyte attractant, is a member of the CC chemokine subfamily. MCP-1 exerts its effects through binding to G-protein-coupled receptors on the surface of leukocytes targeted for activation and migration. Role of MCP-1 and its receptor CCR2 in monocyte recruitment during infection or under other inflammatory conditions is well known.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the role of MCP-1 in various allergic conditions, immunodeficiency diseases, bone remodelling, and permeability of blood - brain barrier, atherosclerosis, nephropathies and tumors.

CONCLUSION

MCP-1 plays an important role in pathogenesis of various disease states and hence MCP-1 inhibition may have beneficial effects in such conditions.

Mechanisms of acetaminophen-induced liver necrosis

Although considered safe at therapeutic doses, at higher doses, acetaminophen produces a centrilobular hepatic necrosis that can be fatal. Acetaminophen poisoning accounts for approximately one-half of all cases of acute liver failure in the United States and Great Britain today. The mechanism occurs by a complex sequence of events. These events include: (1) CYP metabolism to a reactive metabolite which depletes glutathione and covalently binds to proteins; (2) loss of glutathione with an increased formation of reactive oxygen and nitrogen species in hepatocytes undergoing necrotic changes; (3) increased oxidative stress, associated with alterations in calcium homeostasis and initiation of signal transduction responses, causing mitochondrial permeability transition; (4) mitochondrial permeability transition occurring with additional oxidative stress, loss of mitochondrial membrane potential, and loss of the ability of the mitochondria to synthesize ATP; and (5) loss of ATP which leads to necrosis. Associated with these essential events there appear to be a number of inflammatory mediators such as certain cytokines and chemokines that can modify the toxicity. Some have been shown to alter oxidative stress, but the relationship of these modulators to other critical mechanistic events has not been well delineated. In addition, existing data support the involvement of cytokines, chemokines, and growth factors in the initiation of regenerative processes leading to the reestablishment of hepatic structure and function.

Dengue virus pathogenesis: an integrated view

Much remains to be learned about the pathogenesis of the different manifestations of dengue virus (DENV) infections in humans. They may range from subclinical infection to dengue fever, dengue hemorrhagic fever (DHF), and eventually dengue shock syndrome (DSS). As both cell tropism and tissue tropism of DENV are considered major determinants in the pathogenesis of dengue, there is a critical need for adequate tropism assays, animal models, and human autopsy data. More than 50 years of research on dengue has resulted in a host of literature, which strongly suggests that the pathogenesis of DHF and DSS involves viral virulence factors and detrimental host responses, collectively resulting in abnormal hemostasis and increased vascular permeability. Differential targeting of specific vascular beds is likely to trigger the localized vascular hyperpermeability underlying DSS. A personalized approach to the study of pathogenesis will elucidate the basis of individual risk for development of DHF and DSS as well as identify the genetic and environmental bases for differences in risk for development of severe disease.

Cathepsin G-mediated enhanced TGF-beta signaling promotes angiogenesis via upregulation of VEGF and MCP-1

Transforming growth factor (TGF)-beta signaling makes a significant contribution to the pathogenesis of breast cancer bone metastasis. In other tumor types, TGF-beta has been shown to promote tumor vascularity. Here, we report that inhibition of TGF-beta significantly reduces microvessel density in mammary tumor-induced bone lesions, mediated by decreased expression of both vascular endothelial growth factor (VEGF) and monocyte chemotactic protein (MCP)-1, both known angiogenic factors. Cathepsin G upregulation at the tumor-bone interface has been linked to increased TGF-beta signaling, and we also report that inhibition of Cathepsin G reduced tumor vascularity, as well as VEGF and MCP-1 expression.

Soluble Flt-1 gene transfer ameliorates neointima formation after wire injury in flt-1 tyrosine kinase-deficient mice

OBJECTIVE

We have demonstrated that vascular endothelial growth factor (VEGF) expression is upregulated in injured vascular wall, and blockade of VEGF inhibited monocyte infiltration and neointima formation in several animal models. In the present study, we aimed to clarify relative role of two VEGF receptors, flt-1 versus flk-1/KDR, in neointima formation after injury using flt-1 tyrosine kinase-deficient (Flt-1 TK(-/-)) mice and soluble Flt-1(sFlt-1) gene transfer.

METHODS AND RESULTS

Neointima formation was comparable between wild-type and Flt-1 TK(-/-) mice 28 days after intraluminal wire injury in femoral arteries. By contrast, neointima formation was significantly suppressed by sFlt-1 gene transfer into Flt-1 TK(-/-) mice that blocks VEGF action on flk-1 (intima/media ratio: 2.8+/-0.4 versus 1.4+/-0.4, P<0.05). The inhibition of neointima formation was preceded by significant reduction of monocyte chemoattractant protein (MCP-1) expression in vascular smooth muscle cells (VSMCs) and monocyte infiltration 7 days after injury. Gene transfer of sFlt-1 or treatment of flk-1-specific antibody significantly inhibited VEGF-induced MCP-1 expression determined by RT-PCR in cultured aortic tissue and VSMCs. MCP-1-induced chemotaxis was equivalent between wild-type and Flt-1 TK(-/-) mice.

CONCLUSIONS

These results suggest that endogenous VEGF accelerates neointima formation through flk-1 by regulating MCP-1 expression in VSMCs and macrophage-mediated inflammation in injured vascular wall in murine model of wire injury.

Elevated VEGF-plasma levels in young patients with mild essential hypertension

BACKGROUND

Growing evidence shows that inflammation plays a pivotal role in the pathophysiology of essential hypertension (EH). Vascular endothelial cell growth factor (VEGF) is currently discussed as a possible mediator of inflammation. To investigate the hypothesis that VEGF plays a role as an inflammatory mediator in EH we performed the present pilot study of young patients in a very early stage of EH.

MATERIALS AND METHODS

15 young patients with mild EH [33.8 +/- 7.3 years, systolic blood pressure (SBP): 143.8 +/- 10.5 mmHg, diastolic blood pressure (DBP): 88.2 +/- 11.1 mmHg, mean arterial pressure (MAP) 106.6 +/- 10.4 mmHg] and 15 healthy controls (31.7 +/- 10.6 years) were examined. Blood was drawn from a peripheral vein and serum levels of VEGF, monocyte-chemoattractant-protein (MCP)-1, high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, and tumour-necrosis-factor (TNF)-alpha were measured via commercially available enzyme-linked immunoassays.

RESULTS

Hypertensives showed increased plasma levels of VEGF (P < 0.05) and MCP-1 (P < 0.05). VEGF positively correlated with MAP (r = 0.46, P < 0.05) and MCP-1 (r = 0.63, P < 0.01). Multivariate analysis demonstrated VEGF to be an independent predictor of MCP-1 levels. Furthermore, hypertensives had higher levels of hsCRP (P < 0.01), IL-6 (P < 0.001) and TNF-alpha (P < 0.05). IL-6 levels correlated with SBP (r = 0.59, P < 0.001), DBP (r = 0.67, P < 0.001) and MAP (r = 0.46, P < 0.001). A significant positive correlation was also found between hsCRP levels and SBP (r = 0.39, P < 0.05).

CONCLUSIONS

This pilot study demonstrates that in an early state of EH, inflammatory pathways have already been activated. Besides classical pro-inflammatory cytokines, VEGF serum levels are significantly elevated. The positive correlation of VEGF with MCP-1 is suggestive for the already described induction of MCP-1 via VEGF.

Concomitant expression of the chemokines RANTES and MCP-1 in human breast cancer: a basis for tumor-promoting interactions

The chemokines RANTES (CCL5) and MCP-1 (CCL2) were suggested to contribute, independently, to breast malignancy. In the present study, we asked if the two chemokines are jointly expressed in clinical samples of breast cancer patients, and do they interact in breast tumor cells. We found that RANTES and MCP-1 were expressed by breast tumor cells in primary tumors of Ductal Carcinoma In Situ and of Invasive Ductal Carcinoma, but minimally in normal breast epithelial duct cells. The chemokines were also detected in metastases and pleural effusions. Novel findings showed that co-expression of RANTES and MCP-1 in the same tumor was associated with more advanced stages of disease, suggesting that breast tumors "benefit" from interactions between the two chemokines. Accordingly, MCP-1 significantly promoted the release of RANTES from endogenous pre-made vesicles, in an active process that depended on calcium from intracellular and extracellular sources, and on intracellular transport of RANTES towards exocytosis. Our findings show a chemokine-triggered release of stored pro-malignancy chemokine from breast tumor cells. These observations support a major tumor-promoting role for co-expression of the chemokines in breast malignancy, and agree with the significant association of joint RANTES and MCP-1 expression with advanced stages of breast cancer.

CD34+ cells augment endothelial cell differentiation of CD14+ endothelial progenitor cells in vitro

Neovascularization by endothelial progenitor cells (EPC) for the treatment of ischaemic diseases has been a topic of intense research. The CD34(+) cell is often designated as EPC, because it contributes to repair of ischaemic injuries through neovascularization. However, incorporation of CD34(+) cells into the neovasculature is limited, suggesting another role which could be paracrine. CD14(+) cells can also differentiate into endothelial cells and contribute to neovascularization. However, the low proliferative capacity of CD14(+) cell-derived endothelial cells hampers their use as therapeutic cells. We made the assumption that an interaction between CD34(+) and CD14(+) cells augments endothelial differentiation of the CD14(+) cells. In vitro, the influence of CD34(+) cells on the endothelial differentiation capacity of CD14(+) cells was investigated. Endothelial differentiation was analysed by expression of endothelial cell markers CD31, CD144, von Willebrand Factor and endothelial Nitric Oxide Synthase. Furthermore, we assessed proliferative capacity and endothelial cell function of the cells in culture. In monocultures, 63% of the CD14(+)-derived cells adopted an endothelial cell phenotype, whereas in CD34(+)/CD14(+) co-cultures 95% of the cells showed endothelial cell differentiation. Proliferation increased up to 12% in the CD34(+)/CD14(+) co-cultures compared to both monocultures. CD34-conditioned medium also increased endothelial differentiation of CD14(+) cells. This effect was abrogated by hepatocyte growth factor neutralizing antibodies, but not by interleukin-8 and monocyte chemoattractant protein-1 neutralizing antibodies. We show that co-culturing of CD34(+) and CD14(+) cells results in a proliferating population of functional endothelial cells, which may be suitable for treatment of ischaemic diseases such as myocardial infarction.

Functional promoter variant in zinc finger protein 202 predicts severe atherosclerosis and ischemic heart disease

OBJECTIVES

This study was designed to test the hypotheses that single nucleotide polymorphisms (SNPs), in zinc finger protein 202 (ZNF202), predict severe atherosclerosis and ischemic heart disease (IHD).

BACKGROUND

ZNF202 is a transcriptional repressor controlling promoter elements in genes involved in vascular maintenance and lipid metabolism.

METHODS

We first determined genotype association for 9 ZNF202 SNPs with severe atherosclerosis (ankle brachial index >0.7 vs. <or=0.7) in a cross-sectional study of 5,355 individuals from the Danish general population. We then determined genotype association with IHD in 10,431 individuals from the Danish general population, the CCHS (Copenhagen City Heart Study), including 1,511 incident IHD events during 28 years of follow-up. Results were verified in 2 independent case-control studies including, respectively, 942 and 1,549 cases with IHD and 8,998 controls. Finally, we determined whether g.-660A>G altered transcriptional activity of the ZNF202 promoter in vitro.

RESULTS

Cross-sectionally, ZNF202 g.-660 GG versus AA homozygosity predicted an odds ratio for severe atherosclerosis of 2.01 (95% confidence interval [CI]: 1.34 to 3.01). Prospectively, GG versus AA homozygosity predicted a hazard ratio for IHD of 1.21 (95% CI: 1.02 to 1.43). In the 2 case-control studies, the equivalent odds ratios for IHD were 1.29 (95% CI: 1.02 to 1.62) and 1.60 (95% CI: 1.34 to 1.92), confirming the results from the prospective study. Only 2 other SNPs, which were highly correlated with g.-660A>G, also predicted risk of severe atherosclerosis and IHD. Finally, ZNF202 g.-660G versus g.-660A was associated with a 60% reduction in transcriptional activity in vitro, whereas none of the 2 correlated SNPs were predicted to be functional.

CONCLUSIONS

Homozygosity for a common functional promoter variant in ZNF202 predicts severe atherosclerosis and an increased risk of IHD.

Recruitment of the inflammatory subset of monocytes to sites of ischemia induces angiogenesis in a monocyte chemoattractant protein-1-dependent fashion

There is accumulating evidence that delivery of bone marrow cells to sites of ischemia by direct local injection or mobilization into the blood can stimulate angiogenesis. This has stimulated tremendous interest in the translational potential of angiogenic cell population(s) in the bone marrow to mediate therapeutic angiogenesis. However, the mechanisms by which these cells stimulate angiogenesis are unclear. Herein, we show that the inflammatory subset of monocytes is selectively mobilized into blood after surgical induction of hindlimb ischemia in mice and is selectively recruited to ischemic muscle. Adoptive-transfer studies show that delivery of a small number of inflammatory monocytes early (within 48 h) of induction of ischemia results in a marked increase in the local production of MCP-1, which in turn, is associated with a secondary, more robust wave of monocyte recruitment. Studies of mice genetically deficient in MCP-1 or CCR2 indicate that although not required for the early recruitment of monocytes, the secondary wave of monocyte recruitment and subsequent stimulation of angiogenesis are dependent on CCR2 signaling. Collectively, these data suggest a novel role for MCP-1 in the inflammatory, angiogenic response to ischemia.

c-Jun controls histone modifications, NF-kappaB recruitment, and RNA polymerase II function to activate the ccl2 gene

Interleukin-1 (IL-1)-induced mRNA expression of ccl2 (also called MCP-1), a prototypic highly regulated inflammatory gene, is severely suppressed in cells lacking c-Jun or Jun N-terminal protein kinase 1 (JNK1)/JNK2 genes and is only partially restored in cells expressing a c-Jun(SS63/73AA) mutant protein. We used chromatin immunoprecipitation to identify three c-Jun-binding sites located in the far 5' region close to the transcriptional start site and in the far 3' region of murine and human ccl2 genes. Mutational analysis revealed that the latter two sites contribute to ccl2 transcription in response to the presence of IL-1 or of ectopically expressed c-Jun-ATF-2 dimers. Further experiments comparing wild-type and c-Jun-deficient cells revealed that c-Jun regulates Ser10 phosphorylation of histone H3, acetylation of histones H3 and H4, and recruitment of histone deacetylase 3 (HDAC3), NF-kappaB subunits, and RNA polymerase II across the ccl2 locus. c-Jun also coimmunoprecipitated with p65 NF-kappaB and HDAC3. Based on DNA microarray analysis, c-Jun was required for full expression of 133 out of 162 IL-1-induced genes. For inflammatory genes, these data support the idea of an activator function of c-Jun that is executed by multiple mechanisms, including phosphorylation-dependent interaction with p65 NF-kappaB and HDAC3 at the level of chromatin.

The inflammatory chemokines CCL2 and CCL5 in breast cancer

A causal role was recently attributed to inflammation in many malignant diseases, including breast cancer. The different inflammatory mediators that are involved in this disease include cells, cytokines and chemokines. Of these, many studies have addressed the involvement and roles of the inflammatory chemokines CCL2 (MCP-1) and CCL5 (RANTES) in breast malignancy. While minimally expressed by normal breast epithelial duct cells, both chemokines are highly expressed by breast tumor cells at primary tumor sites, indicating that CCL2 and CCL5 expression is acquired in the course of malignant transformation, and suggesting that the two chemokines play a role in breast cancer development and/or progression. Supporting this possibility are findings showing significant associations between CCL2 and CCL5 and more advanced disease course and progression. Furthermore, studies in animal model systems have shown active and causative roles for the two chemokines in this disease. In line with the tumor-promoting roles of CCL2 and CCL5 in breast cancer, the two chemokines were shown to mediate many types of tumor-promoting cross-talks between the tumor cells and cells of the tumor microenvironment: (1) they shift the balance at the tumor site between different leukocyte cell types by increasing the presence of deleterious tumor-associated macrophages (TAM) and inhibiting potential anti-tumor T cell activities; (2) of the two chemokines, mainly CCL2 promotes angiogenesis; (3) CCL2 and CCL5 which are expressed by cells of the tumor microenvironment osteoblasts and mesenchymal stem cells play a role in breast metastatic processes. In addition, both chemokines act directly on the tumor cells to promote their pro-malignancy phenotype, by increasing their migratory and invasion-related properties. Together, the overall current information suggests that CCL2 and CCL5 are inflammatory mediators with pro-malignancy activities in breast cancer, and that they should be considered as potential therapeutic targets for the limitation of this disease.

Local delivery of anti-monocyte chemoattractant protein-1 by gene-eluting stents attenuates in-stent stenosis in rabbits and monkeys

OBJECTIVE

We have previously shown that the intramuscular transfer of the anti-monocyte chemoattractant protein-1 (MCP-1) gene (called 7ND) is able to prevent experimental restenosis. The aim of this study was to determine the in vivo efficacy and safety of local delivery of 7ND gene via the gene-eluting stent in reducing in-stent neointima formation in rabbits and in cynomolgus monkeys.

METHODS AND RESULTS

We here found that in vitro, 7ND effectively inhibited the chemotaxis of mononuclear leukocytes and also inhibited the proliferation/migration of vascular smooth muscle cells. We then coated stents with a biocompatible polymer containing a plasmid bearing the 7ND gene, and deployed these stents in the iliac arteries of rabbits and monkeys. 7ND gene-eluting stents attenuated stent-associated monocyte infiltration and neointima formation after one month in rabbits, and showed long-term inhibitory effects on neointima formation when assessments were carried out at 1, 3, and 6 months in monkeys.

CONCLUSIONS

Strategy of inhibiting the action of MCP-1 with a 7ND gene-eluting stent reduced in-stent neointima formation with no evidence of adverse effects in rabbits and monkeys. The 7ND gene-eluting stent could be a promising therapy for treatment of restenosis in humans.

The chemokine system in arteriogenesis and hind limb ischemia

Chemokines (chemotactic cytokines) are important in the recruitment of leukocytes to injured tissues and, as such, play a pivotal role in arteriogenesis and the tissue response to ischemia. Hind limb ischemia represents a complex model with arteriogenesis (collateral artery formation) occurring in tissues with normal perfusion while areas exhibiting ischemic necrosis undergo angiogenesis and skeletal muscle regeneration; monocytes and macrophages play an important role in all three of these processes. In addition to leukocyte trafficking, chemokines are produced by and chemokine receptors are present on diverse cell types, including myoblasts, endothelial, and smooth muscle cells. Thus, the chemokine system may have direct effects as well as inflammatory-mediated effects on arteriogenesis, angiogenesis, and skeletal muscle regeneration. This article reviews the complexity of the hind limb ischemia model and the role of the chemokine system in arteriogenesis and the tissue response to ischemia. Special emphasis will be placed on the roles of monocytes/macrophages and CCL2/monocyte chemotactic protein-1 (MCP-1) in these processes.

Delayed angiogenesis and VEGF production in CCR2-/- mice during impaired skeletal muscle regeneration

The regulation of vascular endothelial growth factor (VEGF) levels and angiogenic events during skeletal muscle regeneration remains largely unknown. This study examined angiogenesis, VEGF levels, and muscle regeneration after cardiotoxin (CT)-induced injury in mice lacking the CC chemokine receptor 2 (CCR2). Muscle regeneration was significantly decreased in CCR2-/- mice as was the early accumulation of macrophages after injury. In both mouse strains, tissue VEGF was similar at baseline (no injections) and significantly decreased at day 3 post-CT. Tissue VEGF in wild-type (WT) mice was restored within 7 days postinjury but remained significantly reduced in CCR2-/- mice until day 21. Capillary density (capillaries/mm(2)) within regenerating muscle was maximal in WT mice at day 7 and double that of baseline muscle. In comparison, maximal capillary density in CCR2-/- mice occurred at 21 days postinjury. Maximal capillary density developed concurrent with the restoration of tissue VEGF in both strains. A highly significant, inverse relationship existed between the size of regenerated muscle fibers and capillaries per square millimeter. Although this relationship was comparable in WT and CCR2-/- animals, there was a significant decrease in the magnitude of this response in the absence of CCR2, reflecting the observation that regenerated muscle fiber size in CCR2-/- mice was only 50% of baseline at 42 days postinjury, whereas WT mice had attained baseline fiber size by day 21. Thus CCR2-dependent events in injured skeletal muscle, including impaired macrophage recruitment, contribute to restoration of tissue VEGF levels and the dynamic processes of capillary formation and muscle regeneration.

The multifaceted roles of chemokines in malignancy

Tumor development and progression are multifactorial processes, regulated by a large variety of intrinsic and microenvironmental factors. A key role in cancer is played by members of the chemokine superfamily. Chemokines and their receptors are expressed by tumor cells and by host cells, in primary tumors and in specific metastatic loci. The effects of chemokines on tumorigenesis are diverse: While some members of the superfamily significantly support this process, others inhibit fundamental events required for tumor establishment and metastasis. The current review describes the multifaceted roles of chemokines in malignancy, addressing four major aspects of their activities: (1) inducing leukocyte infiltration to tumors and regulating immune functions, with emphasis on tumor-associated macrophages (and the chemokines CCL2, CCL5), T cells (and the chemokines CXCL9, CXCL10) and dendritic cells (and the chemokines CCL19, CCL20, CCL21); (2) directing the homing of tumor cells to specific metastatic sites (the CXCL12-CXCR4 axis); (3) regulating angiogenic processes (mainly the ELR(+)-CXC and non-ELR-CXC chemokines); (4) acting directly on the tumor cells to control their malignancy-related functions. Together, these different chemokine functions establish a net of interactions between the tumor cells and their microenvironment, and partly dictate the fate of the malignancy cascade.

MCP-1, a highly expressed chemokine in dengue haemorrhagic fever/dengue shock syndrome patients, may cause permeability change, possibly through reduced tight junctions of vascular endothelium cells

Vascular leakage, one hallmark of dengue haemorrhagic fever (DHF) and dengue shock syndrome, has been linked to the mediators secreted from cells in the circulatory system. In this study, extremely high expression levels of monocyte chemoattractant protein-1 (MCP-1) were found in the plasma of DHF patients compared with low MCP-1 expression levels in the plasma of enterovirus 71-infected patients. It was also found that MCP-1 expression was induced in dengue virus 2 (DV2)-infected monocytes and lymphocytes, but not in liver or endothelial cells. Exposing monolayers of human umbilical vein endothelial cells (HUVECs) to recombinant human MCP-1 (rhMCP-1) or to the culture supernatant of DV2-infected human monocytes increased the vascular permeability of the cells. MCP-1-neutralizing monoclonal antibody only partially prevented monolayer permeability change. Consistently, the distribution of the tight junction protein ZO-1 on the cellular membranes of HUVECs was disrupted by rhMCP-1 or by the conditioned medium of DV2-infected monocytes. In summary, it was found that the increased permeability and disrupted tight junctions of human vascular endothelium cells were effected through a mechanism partially dependent on MCP-1, which was secreted by DV2-infected monocytes and lymphocytes.

Monocytic/macrophagic pneumonitis after intrabronchial deposition of vascular endothelial growth factor in neonatal lambs

Preterm and young neonates are prone to inadequate surfactant production and are susceptible to respiratory distress syndrome characterized by alveolar damage and hyaline-membrane formation. Glucocorticoid therapy is commonly used in preterm and young infants to enhance lung maturation and surfactant synthesis. Recently, vascular endothelial growth factor (VEGF) was suggested to be a novel therapeutic agent for lung maturation that lacked adverse effects in mice. The purpose of this study was to assess the safety of incremental concentration (0.0005, 0.005, and 0.05 mg/ml) and duration (16, 24, and 32 hours) of recombinant human VEGF after bronchoscopic instillation (10 ml) in neonatal lambs. High-dose VEGF caused locally extensive plum-red consolidation that was microscopically characterized by interstitial and alveolar infiltrates of cells that were morphologically and phenotypically (CD68+) consistent with monocytes/macrophages. T cells (CD3+) and B cells (CD79+) were located primarily in bronchus/bronchiole-associated lymphoid tissue and were not consistently altered by treatment with VEGF. The dose of VEGF had significant effects on both gross lesions (P < .0047) and microscopic monocyte/macrophage recruitment scores (P < .0001). Thus, the VEGF dose instilled into the lung greatly influenced cellular recruitment and lesion development. The post-dosing interval of VEGF in this study had minor impact (no statistical significance) on cellular recruitment. This study showed that airway deposition of VEGF in the neonatal lamb induces monocyte/macrophage recruitment to the lung and high doses can cause severe lesions. The cellular recruitment suggests further research is needed to define dosages that are efficacious in enhancing lung maturation while minimizing potential adverse effects.

MCP-1 mediates TGF-beta-induced angiogenesis by stimulating vascular smooth muscle cell migration

Transforming growth factor-beta (TGF-beta) and its signaling mediators play crucial roles in vascular formation. Our previous microarray analysis identified monocyte chemoattractant protein-1 (MCP-1) as a TGF-beta target gene in endothelial cells (ECs). Here, we report that MCP-1 mediates the angiogenic effect of TGF-beta by recruiting vascular smooth muscle cells (VSMCs) and mesenchymal cells toward ECs. By using a chick chorioallantoic membrane assay, we show that TGF-beta promotes the formation of new blood vessels and this promotion is attenuated when MCP-1 activity is blocked by its neutralizing antibody. Wound healing and transwell assays established that MCP-1 functions as a chemoattractant to stimulate migration of VSMCs and mesenchymal 10T1/2 cells toward ECs. Furthermore, the conditioned media from TGF-beta-treated ECs stimulate VSMC migration, and inhibition of MCP-1 activity attenuates TGF-beta-induced VSMC migration toward ECs. Finally, we found that MCP-1 is a direct gene target of TGF-beta via Smad3/4. Taken together, our findings suggest that MCP-1 mediates TGF-beta-stimulated angiogenesis by enhancing migration of mural cells toward ECs and thus promoting the maturation of new blood vessels.

Nonendothelial mesenchymal cell-derived MCP-1 is required for FGF-2-mediated therapeutic neovascularization: critical role of the inflammatory/arteriogenic pathway

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is a C-C chemokine that is known as an inflammatory/arteriogenic factor. Angiogenesis contributes to the inflammatory process; however, the molecular and cellular mechanisms of the links among the inflammatory pathway, arteriogenesis, and angiogenesis have not been well elucidated.

METHODS AND RESULTS

Using murine models of fibroblast growth factor-2 (FGF-2)-mediated therapeutic neovascularization, we here show that FGF-2 targets nonendothelial mesenchymal cells (NEMCs) enhancing both angiogenic (vascular endothelial growth factor [VEGF]) and arteriogenic (MCP-1) signals via independent signal transduction pathways. Severe hindlimb ischemia stimulated MCP-1 expression that was strongly enhanced by FGF-2 gene transfer, and a blockade of MCP-1 activity via a dominant negative mutant as well as a deficiency of its functional receptor CCR2 resulted in the diminished recovery of blood flow attributable to adaptive and therapeutic neovascularization. Tumor necrosis factor (TNF)-alpha stimulated MCP-1 expression in all cell types tested, whereas FGF-2-mediated upregulation of MCP-1 was found only in NEMCs but not in others, a finding that was not affected by VEGF in vitro and in vivo.

CONCLUSIONS

These results indicate that FGF-2 targets NEMCs independently, enhancing both angiogenic (VEGF) as well as inflammatory/arteriogenic (MCP-1) pathways. Therefore, MCP-1/CCR2 plays a critical role in adaptive and FGF-2-mediated therapeutic neovascularization.

Hypoxia-induced mitogenic factor has proangiogenic and proinflammatory effects in the lung via VEGF and VEGF receptor-2

From a mouse model of hypoxia-induced pulmonary hypertension, we previously found a highly upregulated protein in the lung that we named hypoxia-induced mitogenic factor (HIMF), also known as found in inflammatory zone 1 (FIZZ1), and resistin-like molecule alpha (RELMalpha). However, the mechanisms of HIMF in the pulmonary vascular remodeling remain unknown. We now demonstrate that HIMF promoted cell proliferation, migration, and the production of vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) in pulmonary endothelial cells as well as the production of reactive oxygen species in murine monocyte/macrophage cells. HIMF-induced CD31-positive cell infiltrate in in vivo Matrigel plugs was significantly suppressed by VEGF receptor-2 (VEGFR2) blockade. In ex vivo studies, HIMF stimulated the production of VEGF, MCP-1, and stromal cell-derived factor-1 (SDF-1) in the lung resident cells, and VEGFR2 neutralization significantly suppressed HIMF-induced MCP-1 and SDF-1 production. Furthermore, intravenous injection of HIMF showed marked increase of CD68-positive inflammatory cells in the lungs, and these events were attenuated by VEGFR2 neutralization. Intravenous injection of HIMF also downregulated the expression of VEGFR2 in the lung. These results suggest that HIMF plays critical roles in pulmonary inflammation as well as angiogenesis.

Transforming growth factor-beta1 differentially mediates fibronectin and inflammatory cytokine expression in kidney tubular cells

Transforming growth factor-beta(1) (TGF-beta(1)) is not only an important fibrogenic but also immunomodulatory cytokine in the human kidney. We have recently demonstrated that TGF-beta(1) induces interleukin-8 (IL-8), macrophage chemoattractant protein-1 (MCP-1), and fibronectin production in renal proximal tubular (HK-2) cells. However, the unique dependence of IL-8, MCP-1, and fibronectin on TGF-beta(1) expression is unknown. The TGF-beta(1) gene was effectively silenced in HK-2 cells using small-interference (si) RNA. Basal secretion of IL-8 and MCP-1 decreased (both P < 0.05) but, paradoxically, fibronectin increased (P < 0.05) in TGF-beta(1)-silenced cells compared with cells transfected with nonspecific siRNA. Significant increases were observed in mRNA for the TGF-beta(2) (P < 0.05), TGF-beta(3) (P < 0.05) isoforms and pSmad2 (P < 0.05), which were reflected in protein expression. Concurrent exposure to pan-specific TGF-beta antibody reversed the observed increase in fibronectin expression, suggesting that TGF-beta(2) and TGF-beta(3) isoforms mediate the increased fibronectin expression in TGF-beta(1)-silenced cells. An increase in the DNA binding activity of activator protein-1 (AP-1; P < 0.05) was also observed in TGF-beta(1)-silenced cells. In contrast, nuclear factor-kappaB (NF-kappaB) DNA binding activity was significantly decreased (P < 0.0005). These studies demonstrate that TGF-beta(1) is a key regulator of IL-8 and MCP-1, whereas fibronectin expression is regulated by a complex interaction between the TGF-beta isoforms in the HK-2 proximal tubular cell line. Decreased expression of TGF-beta(1) reduces chemokine production in association with reduced NF-kappaB DNA binding activity, suggesting that immunomodulatory pathways in the kidney are specifically dependent on TGF-beta(1). Conversely, decreased expression of TGF-beta(1) results in increased TGF-beta(2), TGF-beta(3), AP-1, and pSmad2 that potentially mediates the observed increase in fibronectin.

Zinc Finger Protein 202: a new candidate gene for ischemic heart disease: The Copenhagen City Heart Study

OBJECTIVE

Zinc Finger Protein 202 (ZNF202) is a transcriptional repressor of genes affecting the vascular endothelium as well as lipid metabolism. A phenotype associated with genetic variation in ZNF202 is presently unknown. We tested the hypothesis that a common variant in ZNF202, A154V, predicts risk of ischemic heart disease (IHD), myocardial infarction (MI), and ischemic cerebrovascular disease (ICVD).

METHODS AND RESULTS

We conducted a prospective study of more than 9000 individuals from the general population with 24 years follow-up. In women, age-adjusted hazard ratios in heterozygotes and homozygotes versus non-carriers were 1.2 (95% CI: 1.0-1.5, P = 0.04) and 1.5 (1.1-2.1, P = 0.007) for IHD, 1.5 (1.1-2.1; P = 0.01) and 1.7 (1.1-2.8, P = 0.02) for MI, and 1.3 (1.0-1.8, P = 0.07) and 1.3 (0.8-2.1; P = 0.33) for ICVD. Adjustments for lipids and lipoproteins did not alter these hazard ratios substantially. Genotype did not predict risk in men. Finally, results for IHD were borderline significant (P = 0.06) in an independent case-control study including 933 patients and 8068 controls.

CONCLUSION

This is the first study to suggest that ZNF202 could be a new candidate gene for IHD and MI in the general population.

Hypoxia reduces constitutive and TNF-α-induced expression of monocyte chemoattractant protein-1 in human proximal renal tubular cells

Chronic hypoxia has been reported to be associated with macrophage infiltration in progressive forms of kidney disease. Here, we investigated the regulatory effects of hypoxia on constitutive and TNF-alpha-stimulated expression of monocyte chemoattractant protein-1 (MCP-1) in cultured human proximal renal tubular cells (HPTECs). Hypoxia reduced constitutive MCP-1 expression at the mRNA and protein levels in a time-dependent fashion for up to 48 h. Hypoxia also inhibited MCP-1 up-regulation by TNF-alpha. Treatment with actinomycin D showed that hypoxic down-regulation of MCP-1 expression resulted mainly from a decrease in the transcription but not the mRNA stability. Immunoblot and immunofluorescence analyses revealed that treatment with hypoxia or an iron chelator, desferrioxamine, induced nuclear accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) in HPTECs. Desferrioxamine mimicked hypoxia in the reduction of MCP-1 expression. However, overexpression of a dominant negative form of HIF-1alpha did not abolish the hypoxia-induced reduction of MCP-1 expression in HPTECs. These results suggest that hypoxia is an important negative regulator of monocyte chemotaxis to the renal inflamed interstitium, by reducing MCP-1 expression partly via hypoxia-activated signals other than the HIF-1 pathway.

CD40/CD40 Ligand Signaling in Mouse Cerebral Microvasculature After Focal Ischemia/Reperfusion

BACKGROUND

CD40/CD40 ligand (CD40L) signaling contributes to proinflammatory and prothrombogenic responses in the vasculature. CD40/CD40L expression is elevated in patients after a transient ischemic attack or stroke. The purpose of this study was to investigate the role of CD40/CD40L signaling in cerebral microvascular dysfunction and tissue injury response to middle cerebral artery occlusion (MCAO) and reperfusion.

METHODS AND RESULTS

Intravital fluorescence microscopy was used to visualize the cerebral microcirculation of wild-type (WT), CD40-deficient, and CD40L-deficient mice subjected to 1-hour MCAO and 4-hour reperfusion. The adhesion of platelets and of leukocytes and vascular permeability were measured in postcapillary venules after 4-hour and 1-hour reperfusions, respectively. Cerebral infarct volume was analyzed 24 hours after reperfusion. Platelet and leukocyte adhesion was elevated and blood/brain barrier function was compromised by MCAO in WT mice. Blood cell recruitment and increased permeability were blunted in both CD40-deficient and CD40L-deficient mice. Infarct volume was also reduced in CD40- and CD40L-deficient mice compared with WT mice.

CONCLUSIONS

Our findings indicate that CD40/CD40L signaling contributes to inflammatory and prothrombogenic responses and brain infarction induced by MCAO and reperfusion. The CD40/CD40L dyad may play a significant pathogenic role in the acute phase of ischemic stroke.

Quantification and functional analysis of chemotaxis by laser scanning cytometry

BACKGROUND

Evaluation of chemotaxis assays traditionally relies on cumbersome and at times inaccurate visual counting. Moreover, many physiologic parameters that could be evaluated in conjunction with chemotactic migration, aside from morphologic changes, usually are not assessed due to the lack of a simultaneous method of analysis. We tested the suitability of laser scanning cytometry (LSC) as a convenient platform for counting migrated cells and for concurrent analysis of some features associated with their physiologic status.

METHODS

We induced migration of THP-1 monocytes across Nuclepore filters with monocyte chemotactic protein-1 or vascular endothelial growth factor, alone or in combination. Filters were collected, and cells were fixed on filters and stained with the nuclear stain propidium iodide. Chemotactic indices were obtained by counting representative microscopic fields and by scanning the filters in LSC mode.

RESULTS

We found an excellent correlation between direct counting and LSC. In addition, the software tools embodied in the LSC instrument allowed the observation of changes in nuclear compactness (increase in propidium iodide brightness) and morphology (increase in nuclear area and perimeter) that occurred in transmigrated cells. Monocyte chemotactic protein-1 and vascular endothelial growth factor acted as additive stimuli on these parameters.

CONCLUSIONS

LSC analysis of cells undergoing chemotaxis provides a reliable and comprehensive assessment of the numbers and distribution of migrated cells and some of their nuclear parameters. The method can be easily extended to include the assessment of coincident molecular changes in cells due to chemotactic stimulation.

Essential Role of Vascular Endothelial Growth Factor and Flt-1 Signals in Neointimal Formation After Periadventitial Injury

Objective— Vascular endothelial growth factor (VEGF) is upregulated after arterial injury. Its role in the pathogenesis of neointimal formation after periadventitial injury, however, has not been addressed.

Methods and Results— Expression of VEGF and its receptors but not that of placental growth factor markedly increased with the development of neointimal formation in hypercholesterolemic mice after cuff-induced periarterial injury. Transfection with the murine soluble Flt-1 (sFlt-1) gene to block VEGF in vivo in mice inhibited early inflammation and later neointimal formation. The sFlt-1 gene transfer did not affect plasma lipid levels but attenuated increased expression of VEGF, Flt-1, Flk-1, monocyte chemoattractant protein-1, and other inflammation-promoting factors. Mice with Flt-1 kinase deficiency also displayed reduced neointimal formation.

Conclusions— Inflammatory changes mediated by VEGF and Flt-1 signals play an important role in the pathogenesis of neointimal formation after cuff-induced periadventitial injury. VEGF might promote neointimal formation by acting as a proinflammatory cytokine.

Possible new role of monocyte chemoattractant protein-1 in hemodialysis patients with cardiovascular disease

AIMS

Reactive oxygen species have been implicated in increased vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein (MCP-1) levels in vascular cells, which may promote atherosclerosis progression.

METHODS

We studied the association between pre-dialysis plasma levels of VEGF and MCP-1 in 45 hemodialysis (HD) patients with and without cardiovascular disease (CVD) in conditions of increased oxidative stress (SOX).

RESULTS

Compared to the controls, HD patients, especially those with CVD, showed a significant increase in plasma concentrations of Cu/Zn superoxide dismutase (Cu/Zn SOD), C-reactive protein (CRP), MCP-1 and VEGF. The levels of CRP, MCP-1 and VEGF were more increased in patients with CVD than in patients without CVD (all p < 0.01). VEGF strongly and positively correlated with MCP-1 only in HD patients with CVD. Additionally, both VEGF and MCP-1 were associated with Cu/Zn SOD in the whole HD group.

CONCLUSION

For the first time our data indicate a correlation between VEGF and MCP-1 levels in HD patients with CVD in conditions of increased SOX. This interaction may reflect the new role of MCP-1 as an arteriogenic factor in HD patients with CVD.

Monocyte chemoattractant protein-1-induced angiogenesis is mediated by vascular endothelial growth factor-A

Monocyte chemoattractant protein-1 (MCP-1) has been recognized as an angiogenic chemokine. In the present study, we investigated the detailed mechanism by which MCP-1 induces angiogenesis. We found that MCP-1 up-regulated hypoxia-inducible factor 1 alpha (HIF-1 alpha) gene expression in human aortic endothelial cells (HAECs), which induced vascular endothelial growth factor-A(165) (VEGF-A(165)) expression in the aortic wall and HAECs through activation of p42/44 mitogen-activated protein kinase (MAPK). In vivo angiogenesis assay using chick chorioallantoic membrane (CAM) showed that MCP-1-induced angiogenesis was as potent as that induced by VEGF-A(165) and completely inhibited by a VEGF inhibitor, Flt(2-11). The inhibition of RhoA small G protein did not affect MCP-1-induced VEGF-A(165) production and secretion but completely blocked both MCP-1- and VEGF-A-induced new vessel formation, as determined by CAM assay. These results suggest that MCP-1-induced angiogenesis is composed largely of 2 sequential steps: the induction of VEGF-A gene expression by MCP-1 and the subsequent VEGF-A-induced angiogenesis.

Blockade of Vascular Endothelial Growth Factor Suppresses Experimental Restenosis After Intraluminal Injury by Inhibiting Recruitment of Monocyte Lineage Cells

Background— Therapeutic angiogenesis by delivery of vascular endothelial growth factor (VEGF) has attracted attention. However, the role and function of VEGF in experimental restenosis (neointimal formation) after vascular intraluminal injury have not been addressed.

Methods and Results— We report herein that blockade of VEGF by soluble VEGF receptor 1 ( sFlt-1 ) gene transfer attenuated neointimal formation after intraluminal injury in rabbits, rats, and mice. sFlt-1 gene transfer markedly attenuated the early vascular inflammation and proliferation and later neointimal formation. sFlt-1 gene transfer also inhibited increased expression of inflammatory factors such as monocyte chemoattractant protein-1 and VEGF. Intravascular VEGF gene transfer enhanced angiogenesis in the adventitia but did not reduce neointimal formation.

Conclusions— Increased expression and activity of VEGF are essential in the development of experimental restenosis after intraluminal injury by recruiting monocyte-lineage cells.

Vascular endothelial growth factor - basic science and its clinical implications

Vascular endothelial growth factor (VEGF) is the most important signaling molecule involved in the regulation of the formation of new vessels. Results of recent studies have provided new insights into the molecular mechanisms of the VEGF signaling pathways. VEGF local or systemic application represents a new approach in the therapy of ischemic diseases, especially of the coronary artery disease. Inhibition of the VEGF action on various levels is, on the other hand, assumed to be a promising therapeutic concept against cancer. Moreover, VEGF has been recently shown to be associated with some other physiological and pathophysiological processes. In this article we summarize the latest results of VEGF related studies and present the concluding theoretical resource for further research on the role of VEGF in understanding of pathophysiology of diseases and in therapeutic interventions in clinical biomedicine.