Innate Immunity and Angiogenesis

TLR4 stimulation by LPS enhances angiogenesis in a co-culture system consisting of primary human osteoblasts and outgrowth endothelial cells

The development of new approaches leading to fast and successful vascularization of tissue-engineered constructs is one of the most intensively studied subjects in tissue engineering and regenerative medicine. Recently, TLR4 activation and LPS stimulation of endothelial cells have been reported to promote angiogenesis in a variety of settings. In this study, we demonstrate that TLR4 activation by Ultrapure LPS Escherichia coli 0111:B4 (LPS-EB) significantly enhances microvessel formation in a co-culture system consisting of outgrowth endothelial cells (OECs) and primary human osteoblasts (pOBs). The precise modes of TLR4 action on the process of angiogenesis have also been investigated in this study. Using quantitative fluorescence microscopy in monocultures of OECs and pOBs, it was found that TLR4 activation through LPS-EB upregulates the expression level of TLR4/MYD88 and enhances both angiogenesis and osteogenesis. Furthermore, ELISA and qRT-PCR have shown that the level of two adhesion molecules (ICAM-1 and E-selectin), two cytokines (IL-6 and IL-8) and two growth factors (VEGF and PDGF-BB) related to angiogenesis increase significantly after LPS-EB treatment. This increased understanding of the role of TLR4 in angiogenesis could be of value in various settings related to tissue repair and tissue engineering. Moreover, since LPS and TLR4 agonists improve angiogenesis and osteogenesis, TLR4 agonists (endogenous or synthetic) could be used for angiogenesis intervention in vivo and therefore could be tested for their potential clinical applications in promoting angiogenesis in bone tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.

Seeing through VEGF: innate and adaptive immunity in pathological angiogenesis in the eye

The central role of vascular endothelial growth factor (VEGF) signaling in regulating normal vascular development and pathological angiogenesis has been documented in multiple studies. Ocular anti-VEGF therapy is highly effective for treating a subset of patients with blinding eye disorders such as diabetic retinopathy and neovascular age-related macular degeneration (AMD). However, chronic VEGF suppression can lead to adverse effects associated with poor visual outcomes due to the loss of prosurvival and neurotrophic capacities of VEGF. In this review, we discuss emerging evidence for immune-related mechanisms that regulate ocular angiogenesis in a VEGF-independent manner. These novel molecular and cellular pathways may provide potential therapeutic avenues for a multitarget strategy, preserving the neuroprotective functions of VEGF in those patients whose disease is unresponsive to VEGF neutralization.

TLR2 and TLR4 mediate differential responses to limb ischemia through MyD88-dependent and independent pathways

Introduction

The danger signal HMGB1 is released from ischemic myocytes, and mediates angiogenesis in the setting of hindlimb ischemia. HMGB1 is a ligand for innate immune receptors TLR2 and TLR4. While both TLR2 and TLR4 signal through myeloid differentiation factor 88 (MyD88), TLR4 also uniquely signals through TIR-domain-containing adapter-inducing interferon-β (TRIF). We hypothesize that TLR2 and TLR4 mediate ischemic myocyte regeneration and angiogenesis in a manner that is dependent on MyD88 signaling.

Methods

Mice deficient in TLR2, TLR4, MyD88 and TRIF underwent femoral artery ligation in the right hindlimb. Laser Doppler perfusion imaging was used to assess the initial degree of ischemia and the extent of perfusion recovery. Muscle regeneration, necrosis and fat replacement at 2 weeks post-ligation were assessed histologically and vascular density was quantified by immunostaining. In vitro, endothelial tube formation was evaluated in matrigel in the setting of TLR2 and TLR4 antagonism.

Results

While control and TLR4 KO mice demonstrated prominent muscle regeneration, both TLR2 KO and TRIF KO mice exhibited marked necrosis with significant inflammatory cell infiltrate. However, MyD88 KO mice had a minimal response to the ischemic insult with little evidence of injury. This observation could not be explained by differences in perfusion recovery which was similar at two weeks in all the strains of mice. TLR2 KO mice demonstrated abnormal vessel morphology compared to other strains and impaired tube formation in vitro.

Discussion

TLR2 and TRIF signaling are necessary for muscle regeneration after ischemia while MyD88 may instead mediate muscle injury. The absence of TLR4 did not affect muscle responses to ischemia. TLR4 may mediate inflammatory responses through MyD88 that are exaggerated in the absence of TLR2. Additionally, the actions of TLR4 through TRIF may promote regenerative responses that are required for recovery from muscle ischemia.

Preferential colonization of metastases by oncolytic vaccinia virus strain GLV-1h68 in a human PC-3 prostate cancer model in nude mice

Recently, we showed that the oncolytic vaccinia virus GLV-1h68 has a significant therapeutic potential in treating lymph node metastases of human PC-3 prostate carcinoma in tumor xenografts. In this study, underlying mechanisms of the virus-mediated metastases reduction were analyzed. Immunohistochemistry demonstrated that virus-treatment resulted in a drastically decrease of blood and lymph vessels, representing essential routes for PC-3 cell migration, in both tumors and metastases. Thus, GLV-1h68 drastically reduced essential routes for the metastatic spread of PC-3 cells. Furthermore, analysis of viral distribution in GLV-1h68-injected tumor-bearing mice by plaque assays, revealed significantly higher virus titers in metastases compared to solid tumors. To elucidate conditions potentially mediating the preferential viral colonization and eradication of metastases, microenvironmental components of uninfected tumors and metastases were compared by microscopic studies. These analyses revealed that PC-3 lymph node metastases showed increased vascular permeability, higher proliferation status of tumor cells as determined by BrdU- and Ki-67 assays and lesser necrosis of PC-3 cells than solid tumors. Moreover, an increased number of immune cells (MHCII(+)/CD68(+) macrophages, MHCII(+)/CD19(+) B lymphocytes) combined with an up-regulated expression of pro-inflammatory cytokines was observed in metastases in comparison to primary PC-3 tumors. We propose that these microenvironmental components mediated the metastatic tropism of GLV-1h68. Therefore, vaccinia virus-based oncolytic virotherapy might offer a novel treatment of metastatic prostate carcinomas in humans.

Toll-like receptor 4 has an essential role in early skin wound healing

Toll-like receptor 4 (TLR4) has a key role in the initiation of innate immunity and in the regulation of adaptive immune responses. Using microarray analysis and PCR, TLR4 expression was observed to increase in murine skin wounds at the early stages. The cellular location of TLR4 was primarily in keratinocytes at the wound edges. The closure of excisional wounds was significantly delayed in TLR4-deficient (C3H/HeJ) as compared with wild-type mice, and both IL-1β and IL-6 production were significantly lower in the wounds of TLR4-deficient mice. EGF also markedly decreased in the wound edge of epidermis in TLR4-deficient mice. In vitro studies confirmed that a wound stimulus induces TLR4 mRNA expression in primary normal human epidermal keratinocytes (NHEK). In vitro injury also induced the phosphorylation of p38 and JNK MAPK (Jun N-terminal kinase mitogen-activated protein kinase) and the expression of IL-1β and tumor necrosis factor-α by NHEK. Blockade of TLR4 delayed NHEK migration and abolished the phosphorylation of p38 and JNK MAPK, and blockade of TLR4 and/or p38/JNK abolished IL-1β production. The results suggest that inflammatory cytokine production by injured NHEK is stimulated via the TLR4-p38 and JNK MAPK signaling pathway. Together, the results provide evidence for a role of TLR4 at sites of injury, and suggest that TLR4 is an important regulator of wound inflammation.

Genetic markers of cardiovascular disease in rheumatoid arthritis

Cardiovascular (CV) disease is the most common cause of premature mortality in patients with rheumatoid arthritis (RA). It is the result of an accelerated atherosclerotic process. Both RA and atherosclerosis are complex polygenic diseases. Besides traditional CV risk factors and chronic inflammation, a number of studies have confirmed the role of genetic factors in the development of the atherogenesis observed in RA. In this regard, besides a strong association between the HLA-DRB1∗04 shared epitope alleles and both endothelial dysfunction, an early step in the atherosclerotic process, and clinically evident CV disease, other polymorphisms belonging to genes implicated in inflammatory and metabolic pathways, located inside and outside the HLA region, such as the 308 variant (G > A, rs1800629) of the TNFA locus, the rs1801131 polymorphism (A > C; position + 1298) of the MTHFR locus, or a deletion of 32 base pairs on the CCR5 gene, seem to be associated with the risk of CV disease in patients with RA. Despite considerable effort to decipher the genetic basis of CV disease in RA, further studies are required to better establish the genetic influence in the increased risk of CV events observed in patients with RA.

Chronic hypoxia stimulates an enhanced response to immune challenge without evidence of an energetic tradeoff

There is broad interest in whether there is a tradeoff between energy metabolism and immune function, and how stress affects immune function. Under hypoxic stress, maximal aerobic metabolism is limited, and other aspects of energy metabolism of animals may be altered as well. Although acute hypoxia appears to enhance certain immune responses, the effects of chronic hypoxia on immune function are largely unstudied. We tested: (1) whether chronic hypoxia affects immune function and (2) whether hypoxia affects the metabolic cost of immune function. First, flow cytometry was used to monitor the peripheral blood immunophenotype of mice over the course of 36 days of hypoxic exposure. Second, hypoxic and normoxic mice were subjected to an adaptive immune challenge via keyhole limpet hemocyanin (KLH) or to an innate immune challenge via lipopolysaccharide (LPS). The resting metabolic rates of mice in all immune challenge treatments were also measured. Although hypoxia had little effect on the peripheral blood immunophenotype, hypoxic mice challenged with KLH or LPS had enhanced immunological responses in the form of higher antibody titers or increased TNF-α production, respectively. Initially, mice exposed to hypoxia had lower metabolic rates, but this response was transitory and resting metabolic rates were normal by the end of the experiment. There was no effect of either immune challenge on resting metabolic rate, suggesting that mounting either the acute phase response or a humoral response is not as energetically expensive as previously thought. In addition, our results suggest that immune responses to chronic and acute hypoxia are concordant. Both forms of hypoxia appear to stimulate both innate and adaptive immune responses.

Blockade of Vascular Endothelial Growth Factor (VEGF) Aggravates the Severity of Acute Graft-versus-host Disease (GVHD) after Experimental Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT)

BACKGROUND

Recent clinical observation reported that there was a significant correlation between change in circulating vascular endothelial growth factor (VEGF) levels and the occurrence of severe acute graft-versus-host disease (GVHD) following allogeneic hematopoietic stem cell transplantation (allo-HSCT), but the action mechanisms of VEGF in GVHD have not been demonstrated.

METHODS

This study investigated whether or not blockade of VEGF has an effect on acute GVHD in a lethally irradiated murine allo-HSCT model of B6 (H-2(b))→B6D2F1 (H-2(b/d)). Syngeneic or allogeneic recipient mice were injected subcutaneously with anti-VEGF peptides, dRK6 (50 µg/dose) or control diluent every other day for 2 weeks (total 7 doses).

RESULTS

Administration of the dRK6 peptide after allo-HSCT significantly reduced survival with greaterclinical GVHD scores and body weight loss. Allogeneic recipients injected with the dRK6 peptide exhibited significantly increased circulating levels of VEGF and expansion of donor CD3(+) T cells on day +7 compared to control treated animals. The donor CD4(+) and CD8(+) T-cell subsets have differential expansion caused by the dRK6 injection. The circulating VEGF levels were reduced on day +14 regardless of blockade of VEGF.

CONCLUSION

Together these findings demonstrate that the allo-reactive responses after allo-HSCT are exaggerated by the blockade of VEGF. VEGF seems to be consumed during the progression of acute GVHD in this murine allo-HSCT model.

High mobility group box 1 promotes endothelial cell angiogenic behavior in vitro and improves muscle perfusion in vivo in response to ischemic injury

OBJECTIVES

The angiogenic drive in skeletal muscle ischemia remains poorly understood. Innate inflammatory pathways are activated during tissue injury and repair, suggesting that this highly conserved pathway may be involved in ischemia-induced angiogenesis. We hypothesize that one of the endogenous ligands for innate immune signaling, high mobility group box 1 (HMGB1), in combination with autophagic responses to hypoxia or nutrient deprivation, plays an important role in angiogenesis.

METHODS

Human dermal microvascular endothelial cells (ECs) were cultured in normoxia or hypoxia (1% oxygen). Immunocytochemical analysis of HMGB1 subcellular localization, evaluation of tube formation, and Western blot analysis of myotubule light-chain 3I (LC3I) conversion to LC3II, as a marker of autophagy, were conducted. 3-Methyladenine (3MA), chloroquine, or rapamycin were administered to inhibit or promote autophagy, respectively. In vivo, a murine hind limb ischemia model was performed. Muscle samples were collected at 4 hours to evaluate for nuclear HMGB1 and at 14 days to examine endothelial density. Perfusion recovery in the hind limbs was calculated by laser Doppler perfusion imaging (LDPI).

RESULTS

Hypoxic ECs exhibited reduced nuclear HMGB1 staining compared with normoxic cells (mean fluorescence intensity, 186.9 ± 17.1 vs 236.0 ± 1.6, P = .01) with a concomitant increase in cytosolic staining. HMGB1 treatment of ECs enhanced tube formation, an angiogenic phenotype of ECs. Neutralization of endogenous HMGB1 markedly impaired tube formation and inhibited LC3II formation. Inhibition of autophagy with 3MA or chloroquine abrogated tube formation, whereas its induction with rapamycin enhanced tubing and promoted HMGB1 translocation. In vivo, ischemic skeletal muscle showed reduced numbers of HMGB1-positive myocyte nuclei compared with nonischemic muscle (34.9% ± 1.9% vs 51.7% ± 2.0%, P < .001). Injection of HMGB1 into ischemic hind limbs increased perfusion recovery by 21% and increased EC density (49.2 ± 4.1 vs 34.2 ± 3.4 ECs/high-powered field, respectively; P = .02) at 14 days compared with control hind limbs.

CONCLUSIONS

Nuclear release of HMGB1 and autophagy occur in ECs in response to hypoxia or serum depletion. HMGB1 and autophagy are necessary and likely play an interdependent role in promoting the angiogenic behavior of ECs. In vivo, HMGB1 promotes perfusion recovery and increased EC density after ischemic injury. These findings suggest a possible mechanistic link between autophagy and HMGB1 in EC angiogenic behavior and support the importance of innate immune pathways in angiogenesis.

The acceleration of wound healing in primates by the local administration of immunostimulatory CpG oligonucleotides

The process of wound healing involves complex interactions between circulating immune cells and local epithelial and endothelial cells. Studies in murine models indicate that cells of the innate immune system activated via their Toll-like receptors (TLR) can accelerate wound healing. This work examines whether immunostimulatory CpG oligodeoxynucleotides (ODN) designed to trigger human immune cells via TLR9 can promote the healing of excisional skin biopsies in rhesus macaques. Results indicate that 'K' type CpG ODN significantly accelerate wound closure in non-human primates (p < 0.05). Contributing to this outcome was a CpG-dependent increase in both the production of basic fibroblast growth factor and in keratinocyte migration. Of interest, IL-1α and TGFα normally present at sites of skin injury facilitated these effects. Current findings support the conclusion that the local administration of CpG ODN may provide an effective strategy for accelerating wound healing in humans.

Multiplex immunoassay of lower genital tract mucosal fluid from women attending an urban STD clinic shows broadly increased IL1ß and lactoferrin

Background

More than one million new cases of sexually transmitted diseases (STDs) occur each day. The immune responses and inflammation induced by STDs and other frequent non-STD microbial colonizations (i.e. Candida and bacterial vaginosis) can have serious pathologic consequences in women including adverse pregnancy outcomes, infertility and increased susceptibility to infection by other pathogens. Understanding the types of immune mediators that are elicited in the lower genital tract by these infections/colonizations can give important insights into the innate and adaptive immune pathways that are activated and lead to strategies for preventing pathologic effects.

Methodology/Principal Findings

32 immune mediators were measured by multiplexed immunoassays to assess the immune environment of the lower genital tract mucosa in 84 women attending an urban STD clinic. IL-3, IL-1ß, VEGF, angiogenin, IL-8, ß2Defensin and ß3Defensin were detected in all subjects, Interferon-α was detected in none, while the remaining mediators were detected in 40% to 93% of subjects. Angiogenin, VEGF, FGF, IL-9, IL-7, lymphotoxin-α and IL-3 had not been previously reported in genital mucosal fluid from women. Strong correlations were observed between levels of TNF-α, IL-1ß and IL-6, between chemokines IP-10 and MIG and between myeloperoxidase, IL-8 and G-CSF. Samples from women with any STD/colonization had significantly higher levels of IL-8, IL-3, IL-7, IL-1ß, lactoferrin and myeloperoxidase. IL-1ß and lactoferrin were significantly increased in gonorrhea, Chlamydia, cervicitis, bacterial vaginosis and trichomoniasis.

Conclusions/Significance

These studies show that mucosal fluid in general appears to be an environment that is rich in immune mediators. Importantly, IL-1ß and lactoferrin are biomarkers for STDs/colonizations providing insights into immune responses and pathogenesis at this mucosal site.

High-mobility group box-1 mediates toll-like receptor 4-dependent angiogenesis

OBJECTIVE

Inflammation is closely linked to angiogenesis, and Toll-like receptors (TLRs) are the key mediators of inflammatory responses. However, the impact of TLRs on angiogenesis is incompletely understood. In this study, we determined the involvement of TLRs in angiogenesis.

METHODS AND RESULTS

In a mouse model of alkali-induced corneal neovascularization (CNV), we found that CNV was attenuated in TLR4-/- but not TLR2-/- mice. Further study revealed that the absence of TLR4 led to decreased production of proangiogenic factors in association with reduced accumulation of macrophages at the site of wounds, which was associated with reduced expression of high-mobility group box-1 (HMGB1) protein, an endogenous ligand for TLR4. Topical application of HMGB1 to the injured cornea promoted CNV with increased macrophage accumulation in wild-type mice but not in TLR4-/- mice. HMGB1 treatment in vitro also promoted the production of proangiogenic factors by mouse macrophages in a TLR4-dependent manner. Furthermore, antagonists of HMGB1 and TLR4 reduced CNV and macrophage recruitment in the injured cornea of wild-type mice.

CONCLUSIONS

Our results suggest that the release of HMGB1 in the wounds initiates TLR4-dependent responses that contribute to neovascularization. Thus, targeting HMGB1-TLR4 signaling cascade may constitute a novel therapeutic approach to angiogenesis-related diseases.

Viral-mediated oncolysis is the most critical factor in the late-phase of the tumor regression process upon vaccinia virus infection

Background

In principle, the elimination of malignancies by oncolytic virotherapy could proceed by different mechanisms - e.g. tumor cell specific oncolysis, destruction of the tumor vasculature or an anti-tumoral immunological response. In this study, we analyzed the contribution of these factors to elucidate the responsible mechanism for regression of human breast tumor xenografts upon colonization with an attenuated vaccinia virus (VACV).

Methods

Breast tumor xenografts were analyzed 6 weeks post VACV infection (p.i.; regression phase) by immunohistochemistry and mouse-specific expression arrays. Viral-mediated oncolysis was determined by tumor growth analysis combined with microscopic studies of intratumoral virus distribution. The tumor vasculature was morphologically characterized by diameter and density measurements and vessel functionality was analyzed by lectin perfusion and extravasation studies. Immunological aspects of viral-mediated tumor regression were studied in either immune-deficient mouse strains (T-, B-, NK-cell-deficient) or upon cyclophosphamide-induced immunosuppression (MHCII⁺-cell depletion) in nude mice.

Results

Late stage VACV-infected breast tumors showed extensive necrosis, which was highly specific to cancer cells. The tumor vasculature in infected tumor areas remained functional and the endothelial cells were not infected. However, viral colonization triggers hyperpermeability and dilatation of the tumor vessels, which resembled the activated endothelium in wounded tissue. Moreover, we demonstrated an increased expression of genes involved in leukocyte-endothelial cell interaction in VACV-infected tumors, which orchestrate perivascular inflammatory cell infiltration. The immunohistochemical analysis of infected tumors displayed intense infiltration of MHCII-positive cells and colocalization of tumor vessels with MHCII⁺/CD31⁺ vascular leukocytes. However, GI-101A tumor growth analysis upon VACV-infection in either immunosuppressed nude mice (MHCII⁺-cell depleted) or in immune-deficient mouse strains (T-, B-, NK-cell-deficient) revealed that neither MHCII-positive immune cells nor T-, B-, or NK cells contributed significantly to VACV-mediated tumor regression. In contrast, tumors of immunosuppressed mice showed enhanced viral spreading and tumor necrosis.

Conclusions

Taken together, these results indicate that VACV-mediated oncolysis is the primary mechanism of tumor shrinkage in the late regression phase. Neither the destruction of the tumor vasculature nor the massive VACV-mediated intratumoral inflammation was a prerequisite for tumor regression. We propose that approaches to enhance viral replication and spread within the tumor microenvironment should improve therapeutical outcome.

Extraluminal factors contributing to inflammatory bowel disease

Many identified and yet unknown factors contribute to the pathogenesis of inflammatory bowel disease (IBD). The genome-wide association studies clearly support the earlier developed concept that IBD occurs in genetically predisposed individuals who are exposed to distinct environmental factors, which together result in dysregulation of the mucosal immune system. Thus, the majority of previous studies have focused on the immune response within the intestinal wall. The present review aims to emphasize the contribution of three extraluminal structures to this inflammatory process, namely the mesenteric fat tissue, the lymphatics and the microvasculature. Broadening our view across the intestinal wall will not only facilitate our understanding of the disease, but will also us to identify future therapeutic targets.

Accelerated wound healing mediated by activation of Toll-like receptor 9

Wound healing is mediated through complex interactions between circulating immune cells and local epithelial and endothelial cells. Elements of the innate immune system are triggered when Toll-like receptors (TLR) are stimulated by their cognate ligands, and previous studies suggest that such interactions can accelerate wound healing. This work examines the effect of treating excisional skin biopsies with immunostimulatory CpG oligodeoxynucleotides (ODN) that trigger via TLR9. Results indicate that CpG (but not control) ODN accelerate wound closure and reduce the total wound area exposed over time by >40% (p<0.01). TLR9 knockout mice, a strain unresponsive to the immunomodulatory effects of CpG stimulation, are unresponsive to ODN treatment and exhibit a general delay in healing when compared with wild-type mice. CpG ODN administration promoted the influx of macrophages to the wound site and increased the production of vascular endothelial growth factor, expediting neovascularization of the wound bed (p<0.01 for both parameters). Stimulation via TLR9 thus represents a novel strategy to accelerate wound healing.

Impact of tumor microenvironment on oncolytic viral therapy

Interactions between tumor cells and their microenvironment have been shown to play a very significant role in the initiation, progression, and invasiveness of cancer. These tumor-stromal interactions are capable of altering the delivery and effectiveness of therapeutics into the tumor and are also known to influence future resistance and re-growth after treatment. Here we review recent advances in the understanding of the tumor microenvironment and its response to oncolytic viral therapy. The multifaceted environmental response to viral therapy can influence viral infection, replication, and propagation within the tumor. Recent studies have unveiled the complicated temporal changes in the tumor vasculature post-oncolytic virus (OV) treatment, and their impact on tumor biology. Similarly, the secreted extracellular matrix in solid tumors can affect both infection and spread of the therapeutic virus. Together, these complex changes in the tumor microenvironment also modulate the activation of the innate antiviral host immune response, leading to quick and efficient viral clearance. In order to combat these detrimental responses, viruses have been combined with pharmacological adjuvants and "armed" with therapeutic genes in order to suppress the pernicious environmental conditions following therapy. In this review we will discuss the impact of the tumor environment on viral therapy and examine some of the recent literature investigating methods of modulating this environment to enhance oncolysis.

Skin graft take rates, granulation, and epithelialization: dependence on myeloid cell hypoxia-inducible factor 1alpha

OBJECTIVE

To compare the "take" rates of skin grafts between myeloid-selective hypoxia-inducible factor (HIF) 1alpha knockout (KO) and wild-type (WT) mice. Production of the alpha subunit of HIF-1alpha is increased in healing wounds, which stimulates expression of vascular endothelial growth factor (VEGF) to promote angiogenesis. Therefore, the take rate of skin grafts may be closely associated with the presence or absence of HIF-1alpha production in the recipient bed.

DESIGN

The percentage of healthy graft areas obtained by planimetry and scores for epithelialization and granulation tissue formation obtained by histopathologic analysis were compared in 12 KO and 12 WT mice following skin grafting.

RESULTS

The graft take rate was significantly impaired in the KO group (P = .009), whereas epithelialization (P = .46) or granulation (P = .41) tissue formation scores did not reveal any significant differences.

CONCLUSION

Hypoxia-inducible factor 1alpha in myeloid cells may be an important molecule for revascularization of avascular tissues such as skin grafts, probably owing to its stimulating effect on angiogenesis.

Complement-mediated inhibition of neovascularization reveals a point of convergence between innate immunity and angiogenesis

Beyond its role in immunity, complement mediates a wide range of functions in the context of morphogenetic or tissue remodeling processes. Angiogenesis is crucial during tissue remodeling in multiple pathologies; however, the knowledge about the regulation of neovascularization by the complement components is scarce. Here we studied the involvement of complement in pathological angiogenesis. Strikingly, we found that mice deficient in the central complement component C3 displayed increased neovascularization in the model of retinopathy of prematurity (ROP) and in the in vivo Matrigel plug assay. In addition, antibody-mediated blockade of C5, treatment with C5aR antagonist, or C5aR deficiency in mice resulted in enhanced pathological retina angiogenesis. While complement did not directly affect angiogenesis-related endothelial cell functions, we found that macrophages mediated the antiangiogenic activity of complement. In particular, C5a-stimulated macrophages were polarized toward an angiogenesis-inhibitory phenotype, including the up-regulated secretion of the antiangiogenic soluble vascular endothelial growth factor receptor-1. Consistently, macrophage depletion in vivo reversed the increased neovascularization associated with C3- or C5aR deficiency. Taken together, complement and in particular the C5a-C5aR axes are potent inhibitors of angiogenesis.

OX40 ligand plays an important role in the development of atherosclerosis through vasa vasorum neovascularization

AIMS

Atherosclerosis is characterized by infiltration of inflammatory cells and enhanced vasa vasorum formation, for which immunological mechanisms may be involved. OX40, a membrane-bound molecule of the tumour necrosis factor-receptor superfamily, is expressed by activated T-cells, while OX40 ligand (OX40L) is expressed in activated macrophages and endothelial cells. In this study, we thus examined whether the OX40/OX40L system is involved in the pathogenesis of atherosclerosis.

METHODS AND RESULTS

We examined apolipoprotein E-deficient (ApoE(-/-)) mice and ApoE(-/-)/OX40L-double-deficient (ApoE(-/-)/OX40L(-/-)) mice fed on a high-fat diet for 8 weeks. The extent of aortic atheroma was significantly less in ApoE(-/-)/OX40L(-/-) mice compared with ApoE(-/-) mice. We also treated high-fat-fed ApoE(-/-) mice with or without MGP34 antibody (OX40L-specific neutralizing antibody) for 10 weeks. After the treatment, the extent of aortic atheroma was again significantly less in MGP34-treated mice compared with controls. Importantly, both vascular density in the aortic adventitia and vascular endothelial growth factor-induced angiogenesis in the Matrigel assay in vivo were significantly reduced in ApoE(-/-)/OX40L(-/-) mice compared with ApoE(-/-) mice. Finally, when high-fat-fed ApoE(-/-) mice were transplanted with bone marrow cells from either wild-type or OX40L(-/-) mice, the extent of aortic atheroma was comparable between the two groups.

CONCLUSION

These results indicate that the vascular OX40/OX40L system plays an important role in the formation of vasa vasorum and subsequent atherosclerosis, suggesting that the vascular OX40/OX40L system might be a new therapeutic target of atherosclerosis.

Assessment of neovascularization within carotid plaques in patients with ischemic stroke

AIM

To assess neovascularization within human carotid atherosclerotic soft plaques in patients with ischemic stroke.

METHODS

Eighty-one patients with ischemic stroke and 95 patients without stroke who had soft atherosclerotic plaques in the internal carotid artery were studied. The thickest soft plaque in each patient was examined using contrast-enhanced ultrasound. Time-intensity curves were collected from 5 s to 3 min after contrast injection. The neovascularization within the plaques in the internal carotid artery was evaluated using the ACQ software built into the scanner by 2 of the experienced investigators who were blinded to the clinical history of the patients.

RESULTS

Ischemic stroke was present in 7 of 33 patients (21%) with grade I plaque, in 14 of 51 patients (28%) with grade II plaque, in 26 of 43 patients (61%) with grade III plaque, and in 34 of 49 patients (69%) with grade IV plaque (P < 0.001 comparing grade IV plaque with grade I plaque and with grade II plaque and P = 0.001 comparing grade III plaque with grade I plaque and with grade II plaque). Analysis of the time intensity curves revealed that patients with ischemic stroke had a significantly higher intensity of enhancement (IE) than those without ischemic stroke (P < 0.01). The wash-in time (WT) of plaque was significantly shorter in stroke patients (P < 0.05). The sensitivity and specificity for IE in the plaque were 82% and 80%, respectively, and for WT were 68% and 74%, respectively. There was no significant difference in the peak intensity or time to peak between the 2 groups.

CONCLUSION

This study shows that the higher the grade of plaque enhancement, the higher the risk of ischemic stroke. The data suggest that the presence of neovascularization is a marker for unstable plaque.

Enhanced TLR4 endothelial cell immunohistochemical expression in symptomatic carotid atherosclerotic plaques

BACKGROUND AND PURPOSE

Toll-like receptor-4 (TLR4) has been linked to the pathogenesis of atherosclerosis. Carotid atheroma endothelial cells (ECs) express TLR4, nevertheless correlations with cerebrovascular symptomatology, epidemiological and clinical variables remain unresolved.

METHODS

Carotid atherosclerotic plaques were obtained by standard carotid endarterectomy from 157 patients with carotid artery disease (84 asymptomatic - Group A, 73 symptomatic - Group B). TLR4 expression was detected by immunohistochemistry and TLR4 positivity, overexpression and intensity of immunostaining in ECs were correlated with cerebrovascular symptomatology, epidemiological and clinical variables.

RESULTS

A significant association was found between TLR4 positivity in ECs and the occurrence of any cerebrovascular event (overall response (OR): 2.85, 95% CI 1.33 - 6.11, p = 0.009). TLR4 overexpression and staining intensity in ECs were both significantly enhanced in symptomatic patients (p < 0.0001 and p = 0.003, respectively). These associations were stronger for the occurrence of a major cerebrovascular accident (CVA) compared with a transient ischemic attack (TIA) or amaurosis fugax. TLR4 expression in ECs was less prominent in statin users (OR: 0.25, 95%CI 0.1 - 0.58, p = 0.001], while it was enhanced in restenotic plaques compared with primary atherosclerotic lesions (p = 0.012).

CONCLUSIONS

TLR4 expression in ECs of carotid atheroma was enhanced in symptomatic patients with most commonly 'unstable' - 'more prone to rupture' carotid plaques.

Incisor degeneration in rats induced by vascular endothelial growth factor/fibroblast growth factor receptor tyrosine kinase inhibition

BMS-645737, an inhibitor of vascular endothelial growth factor (VEGF) receptor-2 and fibroblast growth factor (FGF) receptor-1, has anti-angiogenic activity and was evaluated in nonclinical studies as a treatment for cancer. This article characterizes the BMS-645737-induced clinical, gross, and histologic lesions of incisor teeth in Sprague-Dawley (SD) rats. Rats received 0 800 mg/kg BMS-645737 in a single-dose study or consecutive daily doses of 0 20 mg/kg/day in a 1-month study. The reversibility of these effects was assessed in the 1-month study. White discoloration and fracture of incisors were observed clinically and grossly in the 1-month study. In both studies, dose-dependent histopathologic lesions of incisors were degeneration and/or necrosis of odontoblasts and ameloblasts; decreased mineralization of dentin; inflammation and necrosis of the dental pulp; and edema, congestion, and hemorrhage in the pulp and periodontal tissue adjacent to the enamel organ. Partial recovery was observed at lower doses after a two-week dose-free period in the one-month study. Drug-induced incisor lesions were considered to be related to the pharmacologic inhibitory effects on VEGF and FGF signaling, that is, inhibition of growth and maintenance of small-diameter vessels that support the formation of dentin and enamel in growing teeth and/or to perturbances of function of odontoblasts and ameloblasts or their precursors.

Toll-like receptor 2/6 stimulation promotes angiogenesis via GM-CSF as a potential strategy for immune defense and tissue regeneration

Toll-like receptors (TLRs) are known primarily as pathogen recognition receptors of the innate immunity, initiating inflammatory pathways to organize the immune defense. More recently, an involvement of TLRs in various physiologic and pathologic processes has been reported. Because many of these processes implicate angiogenesis, we here elucidated the role of a TLR2/6-dependent pathway on angiogenesis using the TLR2/6 agonist macrophage-activating lipopeptide of 2 kDa (MALP-2), a common bacterial lipopeptide. In vivo and in vitro Matrigel assays demonstrated that MALP-2 promoted angiogenesis in a TLR2/6-dependent manner. Moreover, MALP-2 induced endothelial cell proliferation and migration and a strong secretion of granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF release in response to MALP-2 from isolated vascular segments was completely prevented when the endothelium was removed. MALP-2 containing Matrigel implants exhibited vascular structures as well as CD45(+) cells. MALP-2 induced migration of leukocytes and likewise GM-CSF release, particularly from the monocyte population. Inhibition of GM-CSF by siRNA or antibodies suppressed MALP-2-induced angiogenesis in vitro and in vivo. These results clearly identified a TLR2/6-dependent induction of angiogenesis by the bacterial lipopeptide MALP-2, which is mediated by GM-CSF. This might represent a general mechanism to enhance or restore blood flow and recruit immune cells for pathogen defense and tissue regeneration.

Chronic morphine administration delays wound healing by inhibiting immune cell recruitment to the wound site

Patients prescribed morphine for the management of chronic pain, and chronic heroin abusers, often present with complications such as increased susceptibility to opportunistic infections and inadequate healing of wounds. We investigated the effect of morphine on wound-healing events in the presence of an infection in an in vivo murine model that mimics the clinical manifestations seen in opioid user and abuser populations. We show for the first time that in the presence of an inflammatory inducer, lipopolysaccharide, chronic morphine treatment results in a marked decrease in wound closure, compromised wound integrity, and increased bacterial sepsis. Morphine treatment resulted in a significant delay and reduction in both neutrophil and macrophage recruitment to the wound site. The delay and reduction in neutrophil reduction was attributed to altered early expression of keratinocyte derived cytokine and was independent of macrophage inflammatory protein 2 expression, whereas suppression of macrophage infiltration was attributed to suppressed levels of the potent macrophage chemoattractant monocyte chemotactic protein-1. When the effects of chronic morphine on later wound healing events were investigated, a significant suppression in angiogenesis and myofibroblast recruitment were observed in animals that received chronic morphine administration. Taken together, our findings indicate that morphine treatment results in a delay in the recruitment of cellular events following wounding, resulting in a lack of bacterial clearance and delayed wound closure.

Controlling the angiogenic switch in developing atherosclerotic plaques: possible targets for therapeutic intervention

Plaque angiogenesis may have an important role in the development of atherosclerosis. Vasa vasorum angiogenesis and medial infiltration provides nutrients to the developing and expanding intima and therefore, may prevent cellular death and contribute to plaque growth and stabilization in early lesions. However in more advanced plaques, inflammatory cell infiltration, and concomitant production of numerous pro-angiogenic cytokines may be responsible for induction of uncontrolled neointimal microvessel proliferation resulting in production of immature and fragile neovessels similar to that seen in tumour development. These could contribute to development of an unstable haemorrhagic rupture-prone environment. Increasing evidence has suggested that the expression of intimal neovessels is directly related to the stage of plaque development, the risk of plaque rupture, and subsequently, the presence of symptomatic disease, the timing of ischemic neurological events and myocardial/cerebral infarction. Despite this, there is conflicting evidence regarding the causal relationship between neovessel expression and plaque thrombosis with some in vivo experimental models suggesting the contrary and as yet, few direct mediators of angiogenesis have been identified and associated with plaque instability in vivo.In recent years, an increasing number of angiogenic therapeutic targets have been proposed in order to facilitate modulation of neovascularization and its consequences in diseases such as cancer and macular degeneration. A complete knowledge of the mechanisms responsible for initiation of adventitial vessel proliferation, their extension into the intimal regions and possible de-novo synthesis of neovessels following differentiation of bone-marrow-derived stem cells is required in order to contemplate potential single or combinational anti-angiogenic therapies. In this review, we will examine the importance of angiogenesis in complicated plaque development, describe the current knowledge of molecular mechanisms of its initiation and maintenance, and discuss possible future anti-angiogenic therapies to control plaque stability.

Helicobacter pylori Hp(2-20) promotes migration and proliferation of gastric epithelial cells by interacting with formyl peptide receptors in vitro and accelerates gastric mucosal healing in vivo

Helicobacter pylori-derived peptide RpL1 aa 2-20 (Hp(2-20)) in addition to its antimicrobial action exerts several immunomodulatory effects in eukaryotic cells by interacting with formyl peptide receptors (FPRs). It has recently been shown that activation of FPRs facilitates intestinal epithelial cell restitution. We investigated whether Hp(2-20) induces healing of injured gastric mucosa and assessed the mechanisms underlying any such effect. We investigated the expression of FPRs in two gastric epithelial cell lines (MKN-28 and AGS) at mRNA and protein level. To determine whether FPRs were functional we performed chemotaxis experiments and proliferation assays and studied the Hp(2-20)-activated downstream signaling pathway. The effect of Hp(2-20) on mucosal healing was evaluated in rats after indomethacin-induced injury. Here we show that: (1) FPRs were expressed in both cell lines; (2) Hp(2-20) stimulated migration and proliferation of gastric epithelial cells; (3) this effect was specifically mediated by formyl peptide receptor-like 1 (FPRL1) and FPRL2 and was associated with activation of FPR-related downstream signaling pathways; (4) Hp(2-20) up-regulated the expression and secretion of vascular endothelial growth factor; and (5) Hp(2-20) accelerated healing of rat gastric mucosa after injury brought about by indomethacin at both the macroscopic and microscopic levels. In conclusion, by interacting with FRPL1 and FPRL2, H. pylori-derived Hp(2-20) induces cell migration and proliferation, as well as the expression of vascular endothelial growth factor, thereby promoting gastric mucosal healing. This study provides further evidence of the complexity of the relationship between H. pylori and human gastric mucosa, and it suggests that a bacterial product may be used to heal gastric mucosal injury.

Interleukin-33 induces angiogenesis and vascular permeability through ST2/TRAF6-mediated endothelial nitric oxide production

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is emerging as a new regulator of immune responses and inflammatory vascular diseases. Although IL-33 and its cognate receptor ST2 appear to be expressed in vascular cells, the precise role of IL-33 in the vasculature has not been determined. In this study, we report a novel role of IL-33 as a potent endothelial activator, promoting both angiogenesis and vascular permeability. IL-33 increased proliferation, migration, and morphologic differentiation of human endothelial cells, consistently with increased angiogenesis in vivo. IL-33 also increased endothelial permeability with reduced vascular endothelial-cadherin-facilitated cell-cell junctions in vitro and induced vascular leakage in mouse skin. These effects of IL-33 were blocked by knockdown of ST2. Ligation of IL-33 with ST2 rapidly increased endothelial nitric oxide (NO) production through TRAF6-mediated activation of phosphoinoside-3-kinase, Akt, and endothelial NO synthase. Moreover, pharmacologic or genetic blockage of endothelial NO generation resulted in the inhibition of angiogenesis and vascular hyperpermeability induced by IL-33. These data demonstrate that IL-33 promotes angiogenesis and vascular leakage by stimulating endothelial NO production via the ST2/TRAF6-Akt-eNOS signaling pathway. These findings open new perspectives for the role of IL-33 in the pathogenesis of angiogenesis-dependent and inflammatory vascular diseases.

Sonic hedgehog is a potent chemoattractant for human monocytes: diabetes mellitus inhibits Sonic hedgehog-induced monocyte chemotaxis

The aim of the present study was to evaluate the expression of hedgehog (Hh) signaling molecules and the chemotactic activity of Sonic hedgehog (Shh) in monocytes from control (CTR) and diabetic patients with or without coronary artery disease (CAD). Previously several studies demonstrated that exogenous administration of Shh can induce angiogenesis and accelerate repair of ischemic myocardium and skeletal muscles. Blood samples were collected from (1) CTR (n = 25); (2) patients with stable CAD without diabetes mellitus (CAD−DM, n = 10); and (3) with stable CAD with DM (CAD+DM, n = 15). Monocytes were isolated by Percoll gradient and subjected to PCR and chemotaxis analysis. Hh signaling molecules were expressed in human monocytes, and Shh-induced monocyte chemotaxis. Shh-stimulated migration of monocytes from CTR measured 172.5 ± 90% and a maximal stimulation was observed at Shh concentration of 1 μg/ml. However, Shh failed to induce migration of monocytes from CAD+DM (94.3 ± 27%, P < 0.001 vs. CTR). The impaired response to Shh was associated with strong transcriptional upregulation of the receptor Ptc, while expression of downstream molecules was not altered. Moreover, Ptc is strongly expressed in macrophages of human aortic atherosclerotic plaque. Thus, Shh is a potent chemoattractant for monocytes and it activates classical signaling pathways related to migration. The Shh signaling was negatively affected by DM which might be involved in the pathogenesis of DM-related complications.

Novel concepts in atherogenesis: angiogenesis and hypoxia in atherosclerosis

The clinical complications of atherosclerosis are caused by thrombus formation, which in turn results from rupture of an unstable atherosclerotic plaque. The formation of microvessels (angiogenesis) in an atherosclerotic plaque contributes to the development of plaques, increasing the risk of rupture. Microvessel content increases with human plaque progression and is likely stimulated by plaque hypoxia, reactive oxygen species and hypoxia-inducible factor (HIF) signalling. The presence of plaque hypoxia is primarily determined by plaque inflammation (increasing oxygen demand), while the contribution of plaque thickness (reducing oxygen supply) seems to be minor. Inflammation and hypoxia are almost interchangeable and both stimuli may initiate HIF-driven angiogenesis in atherosclerosis. Despite the scarcity of microvessels in animal models, atherogenesis is not limited in these models. This suggests that abundant plaque angiogenesis is not a requirement for atherogenesis and may be a physiological response to the pathophysiological state of the arterial wall. However, the destruction of the integrity of microvessel endothelium likely leads to intraplaque haemorrhage and plaques at increased risk for rupture. Although a causal relation between the compromised microvessel structure and atherogenesis or between angiogenic stimuli and plaque angiogenesis remains tentative, both plaque angiogenesis and plaque hypoxia represent novel targets for non-invasive imaging of plaques at risk for rupture, potentially permitting early diagnosis and/or risk prediction of patients with atherosclerosis in the near future.

Nonimmune cells in inflammatory bowel disease: from victim to villain

Nonimmune cells have traditionally been viewed as target cells of the aberrant inflammatory process present in chronic immune-mediated conditions such as inflammatory bowel disease (IBD). However, the discovery that many of the functions traditionally attributed to immune cells are also performed by nonimmune cells has caused a shift to a multidirectional hypothesis in which nonimmune cells and acellular elements play active roles. Many types of interactions occur within this multidirectional system, and the difficulties associated with modeling these complex interactions currently limit our understanding of the cellular network that occurs in IBD. I describe the current knowledge of the roles played by nonimmune cells in the pathogenesis of IBD, as they emerge as crucial alternative targets for therapeutic intervention.

Bench-to-bedside review: Angiopoietin signalling in critical illness - a future target?

Multiple organ dysfunction syndrome (MODS) occurs in response to major insults such as sepsis, severe haemorrhage, trauma, major surgery and pancreatitis. The mortality rate is high despite intensive supportive care. The pathophysiological mechanism underlying MODS are not entirely clear, although several have been proposed. Overwhelming inflammation, immunoparesis, occult oxygen debt and other mechanisms have been investigated, and – despite many unanswered questions – therapies targeting these mechanisms have been developed. Unfortunately, only a few interventions, usually those targeting multiple mechanisms at the same time, have appeared to be beneficial. We clearly need to understand better the mechanisms that underlie MODS. The endothelium certainly plays an active role in MODS. It functions at the intersection of several systems, including inflammation, coagulation, haemodynamics, fluid and electrolyte balance, and cell migration. An important regulator of these systems is the angiopoietin/Tie2 signalling system. In this review we describe this signalling system, giving special attention to what is known about it in critically ill patients and its potential as a target for therapy.

The inflammatory response to skeletal muscle injury: illuminating complexities

Injury of skeletal muscle, and especially mechanically induced damage such as contusion injury, frequently occurs in contact sports, as well as in accidental contact sports, such as hockey and squash. The large variations with regard to injury severity and affected muscle group, as well as non-specificity of reported symptoms, complicate research aimed at finding suitable treatments. Therefore, in order to increase the chances of finding a successful treatment, it is important to understand the underlying mechanisms inherent to this type of skeletal muscle injury and the cellular processes involved in muscle healing following a contusion injury. Arguably the most important of these processes is inflammation since it is a consistent and lasting response. The inflammatory response is dependent on two factors, namely the extent of actual physical damage and the degree of muscle vascularization at the time of injury. However, long-term anti-inflammatory treatment is not necessarily effective in promoting healing, as indicated by various studies on NSAID treatment. Because of the factors named earlier, human studies on the inflammatory response to contusion injury are limited, but several experimental animal models have been designed to study muscle damage and regeneration. The early recovery phase is characterized by the overlapping processes of inflammation and occurrence of secondary damage. Although neutrophil infiltration has been named as a contributor to the latter, no clear evidence exists to support this claim. Macrophages, although forming part of the inflammatory response, have been shown to have a role in recovery, rather than in exacerbating secondary damage. Several probable roles for this cell type in the second phase of recovery, involving resolution processes, have been identified and include the following: (i) phagocytosis to remove cellular debris; (ii) switching from a pro- to anti-inflammatory phenotype in regenerating muscle; (iii) preventing muscle cells from undergoing apoptosis; (iv) releasing factors to promote muscle precursor cell activation and growth; and (v) secretion of cytokines and growth factors to facilitate vascular and muscle fibre repair. These many different roles suggest that a single treatment with one specific target cell population (e.g. neutrophils, macrophages or satellite cells) may not be equally effective in all phases of the post-injury response. To find the optimal targeted, but time-course-dependent, treatments requires substantial further investigations. However, the techniques currently used to induce mechanical injury vary considerably in terms of invasiveness, tools used to induce injury, muscle group selected for injury and contractile status of the muscle, all of which have an influence on the immune and/or cytokine responses. This makes interpretation of the complex responses more difficult. After our review of the literature, we propose that a standardized non-invasive contusion injury is the ideal model for investigations into the immune responses to mechanical skeletal muscle injury. Despite its suitability as a model, the currently available literature with respect to the inflammatory response to injury using contusion models is largely inadequate. Therefore, it may be premature to investigate highly targeted therapies, which may ultimately prove more effective in decreasing athlete recovery time than current therapies that are either not phase-specific, or not administered in a phase-specific fashion.

Wogonoside inhibits lipopolysaccharide-induced angiogenesis in vitro and in vivo via toll-like receptor 4 signal transduction

Wogonoside, one flavonoid derived from the root of Scutellaria baicalensis Georgi, has been reported for its anti-inflammation activity; however, whether it can inhibit inflammation-induced angiogenesis is still unclear. In the present study, we evaluated the effect of wogonoside on lipopolysaccharide (LPS)-induced angiogenesis in vitro and in vivo. Wogonoside suppressed the LPS-stimulated migration and tube formation of human umbilical vein endothelial cells (HUVECs), as well as microvessel sprouting from rat aortic rings in vitro. Moreover, wogonoside also inhibited LPS-stimulated vessel growth of Chicken chorioallantoic membrane (CAM) in vivo. The mechanism revealed that wogonoside inhibited LPS-induced toll-like receptor 4 (TLR4) up-regulation and its downstream mitogen-activated protein kinases (MAPKs) activation, by decreasing the phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase. The results suggest that wogonoside inhibits LPS-induced angiogenesis both in vitro and in vivo, and that it might have a therapeutic potential for the diseases associated with the development of both inflammation and angiogenesis progress.

Abnormal immunological profile and vaginal microbiota in women prone to urinary tract infections

The host determinants of susceptibility to recurrent urinary tract infections (UTI) are poorly understood. We investigated whether the susceptibility is associated with abnormalities in the immunological defense and further explored the linkage to vaginal microbiota. For this purpose, we compared vaginal, urine, and blood samples collected during a disease-free period from 22 women with recurrent UTI and from 17 controls. In UTI-prone women, interleukin-12 (IL-12) production in peripheral monocytes and myeloid dendritic cells (DCs) was significantly (P < 0.05) enhanced whether measured in relative numbers of IL-12-producing cells or in mean IL-12 production per cell. In contrast, no T-cell polarization was observed. Interestingly, it seemed that the cytokine production of DCs and monocytes did not translate into T-cell activation in the UTI-prone group in a manner similar to that seen with the controls. In vaginal mucosa, UTI-prone women had a lower concentration of tissue repair-associated vascular endothelial growth factor (VEGF) (P = 0.006) and less often had detectable amounts of the chief monocyte and DC chemoattractant, monocyte chemotactic protein 1 (P = 0.005), than the controls. The microbiota of UTI-prone women was characterized by a diminished lactobacillus morphotype composition, with an abnormally high (>3) mean Nugent score of 4.6 compared to 1.7 for the controls (P = 0.003). Normal lactobacillus composition was associated with increased IL-17 and VEGF concentrations in vaginal mucosa. In conclusion, immunological defects and a persistently aberrant microbiota, a lack of lactobacilli in particular, may contribute to susceptibility to recurrent UTI. Further studies of antigen-presenting-cell function and T-cell activation in recurrent UTI are called for.

Contrast-enhanced ultrasound imaging of intraplaque neovascularization in carotid arteries: correlation with histology and plaque echogenicity

OBJECTIVES

This study was designed to evaluate contrast-enhanced ultrasound imaging of carotid atherosclerosis as a clinical tool to study intraplaque neovascularization.

BACKGROUND

Plaque neovascularization is associated with plaque vulnerability and symptomatic disease; therefore, imaging of neovascularization in carotid atherosclerosis may represent a useful tool for clinical risk stratification and monitoring the efficacy of antiatherosclerotic therapies.

METHODS

Thirty-two patients with 52 carotid plaques were studied by standard and contrast-enhanced ultrasound imaging. In 17 of these patients who underwent endarterectomy, the surgical specimen was available for histological determination of microvessel density by CD31/CD34 double staining. Plaque echogenicity and degree of stenosis at standard ultrasound imaging were evaluated for each lesion. Contrast-agent enhancement within the plaque was categorized as absent/peripheral (grade 1) and extensive/internal (grade 2).

RESULTS

In the surgical subgroup, plaques with higher contrast-agent enhancement showed a greater neovascularization at histology (grade 2 vs. grade 1 contrast-agent enhancement: median vasa vasorum density: 3.24/mm(2) vs. 1.82/mm(2), respectively, p = 0.005). In the whole series of 52 lesions, echolucent plaques showed a higher degree of contrast-agent enhancement (p < 0.001). Stenosis degree was not associated with neovascularization at histology or with the grade of contrast-agent enhancement.

CONCLUSIONS

Carotid plaque contrast-agent enhancement with sonographic agents correlates with histological density of neovessels and is associated with plaque echolucency, a well-accepted marker of high risk lesions, but it is unrelated to the degree of stenosis. Contrast-enhanced carotid ultrasound imaging may provide valuable information for plaque risk stratification and for assessing the response to antiatherosclerotic therapies, beyond that provided by standard ultrasound imaging.

Effect of mini-tyrosyl-tRNA synthetase on ischemic angiogenesis, leukocyte recruitment, and vascular permeability

Mini-tyrosyl-tRNA synthetase (mini-TyrRS), the N-terminal domain of tyrosyl-tRNA synthetase, is a recently identified protein released by endothelial cells that exhibits angiogenic and leukocyte chemoattractant, ELR-motif (Glu-Leu-Arg)-dependent activities in vitro. We sought to determine whether exogenous mini-TyrRS exerts these and other cytokine-like actions in physiological and pathological settings in vivo. High-dose mini-TyrRS (600 microg.kg(-1).day(-1)) augmented while low-dose mini-TyrRS (3 microg.kg(-1).day(-1)), unexpectedly, inhibited angiogenesis in the ischemic mouse ear. Enhanced angiogenesis was associated with increased CD45- and CD4-positive leukocyte accumulation. Mini-TyrRS also had biphasic actions on both basal and mustard oil-evoked and VEGF-evoked leakage of Evan's blue dye-albumin in nonischemic ear and in endothelial cell monolayers, that is, low-dose inhibited and high-dose augmented leakage. Mutation of the ELR motif of mini-TyrRS abolished the above activities. Mini-TyrRS was reduced (immunoblot) in extracts of ischemic calf muscle and in thoracic aorta explants exposed to hypoxia or VEGF. Inhibition of VEGF with a soluble Flt1 "trap" protein abolished this hypoxic-induced reduction in mini-TyrRS in aorta explants. These data show that mini-TyrRS has dose-dependent biphasic effects on ischemic angiogenesis and vascular permeability in vivo, that is, antiangiogenic and antipermeability activities at low concentration and proangiogenic, propermeability activities at high concentrations.

Bombesin: a possible role in wound repair

During tissue regeneration and wound healing of the skin, migration, proliferation and differentiation of keratinocytes are important processes. Here we assessed the effect of a neuropeptide, bombesin, on keratinocytes during regeneration from scratch wounding. Bombesin purified from amphibian skin, is homologous of mammalian gastrin-releasing peptide and is active in mammals. Its pharmacological effects mediate various physiological activities: hypertensive action, stimulating action on gastric secretion, hyperglycemic effect or increased insulin secretion. In vitro it shows a hyperproliferative effect on different experimental models and is involved in skin repair. The aim of this study was to elucidate the effect of Bombesin in an in vitro experimental model on a mechanically injured human keratinocyte monolayer. We evaluated different mediators involved in wound repair such as IL-8, TGFbeta, IL-1, COX-2, VEGF and Toll-like receptors 2 and 4 (TLR2 and TLR4). We also studied the effects of bombesin on cell proliferation and motility and its direct effect on wound repair by observing the wound closure after mechanical injury. The involvement of the bombesin receptors neuromedin receptor (NMBR) and gastrin-releasing peptide receptor (GRP-R) was also evaluated. Our data suggest that bombesin may have an important role in skin repair by regulating the expression of healing markers. It enhanced the expression of IL-8, TGFbeta, COX-2 and VEGF. It also enhanced the expression of TLR2, while TLR4 was not expressed. Bombesin also increased cell growth and migration. In addition, we showed that NMBR was more involved in our experimental model compared to GRP-R.

Oncolytic HSV-1 infection of tumors induces angiogenesis and upregulates CYR61

Oncolytic viral therapy is under evaluation for toxicity and efficacy in clinical trials relating to several different tumors. We report a significant increase in the angiogenic index of oncolytic virus (OV)-treated glioma-matrigel implants (2.83-fold, P < 0.02). In a rat intracranial glioma model, large tumors from OV-treated animals were significantly more angiogenic than the phosphate-buffered saline (PBS)-treated control tumors (OV: 101 +/- 21.6; PBS: 19.8 +/- 10; P = 0.0037). Transcript profiling of OV-treated tumors revealed dysregulation of several transcripts involved in glioma angiogenesis. OV-mediated induction of CYR61 gene expression (8.94-fold, P = 0.001) correlated significantly with the presence of OV in tumor tissue in vivo (R = 0.7, P < 0.001). Further, induction of CYR61 mRNA and protein were confirmed in multiple human cancer cell lines and primary human tumor-derived cells in vitro, and in tumor lysate and cerebrospinal fluid (CSF) in vivo. Finally, we show that treatment of glioma cells with Cilengitide, known to counter CYR61-induced integrin activation, significantly suppressed the proangiogenic effect of OV treatment of gliomas (P < 0.05).

Temporin A is effective in MRSA-infected wounds through bactericidal activity and acceleration of wound repair in a murine model

We investigated the effect of topical temporin A in the management of methicillin-resistant strain of Staphylococcus aureus (MRSA)-infected experimental surgical wounds in mice. The wound, cut through the panniculus carnosus of BALB/c mice, was inoculated with 5x10(7) colony-forming units of MRSA. Mice were treated with Allevyn, temporin A-soaked Allevyn, Allevyn and daily intraperitoneal teicoplanin (7mg/kg), temporin A-soaked Allevyn and daily intraperitoneal teicoplanin. Main outcome measurements were: quantitative bacterial culture, histological examination with assessment of micro-vessel density and of vascular endothelial growth factor (VEGF) expression in tissue sections, and VEGF plasma levels alike. Treatment with temporin-A associated with teicoplanin injection significantly reduced bacterial load to 0.85 x 10(1)+/-0.1 x 10(1)CFU/ml. Histological examination showed that infected mice receiving temporin A-soaked Allevyn (with or without teicoplanin) had a higher degree of granulation tissue formation and collagen deposition compared to the other treated groups. A significant increase in serum VEGF expression was observed in mice receiving temporin A topically and temporin A topically associated with intraperitoneal teicoplanin. In conclusion our results demonstrated that temporin A is effective in the management of infected wounds, by a significant bacterial growth inhibition and acceleration of wound repair process.

VEGF in biological control

Vascular endothelial growth factor A (VEGF-A) belongs to a family of heparin binding growth factors that include VEGF-B, VEGF-C, VEGF-D, and placental-like growth factor (PLGF). First discovered for its ability to regulate vascular endothelial cell permeability, VEGF is a well-known angiogenic factor that is important for vascular development and maintenance in all mammalian organs. The development of molecular tools and pharmacological agents to selectively inhibit VEGF function and block angiogenesis and/or vascular permeability has led to great promise in the treatment of various cancers, macular degeneration, and wound healing. However, VEGF is also important in animals for the regulation of angiogenesis, stem cell and monocyte/macrophage recruitment, maintenance of kidney and lung barrier functions and neuroprotection. In addition to its role in regulating endothelial cell proliferation, migration, and cell survival, VEGF receptors are also located on many non-endothelial cells and act through autrocrine pathways to regulate cell survival and function. The following review will discuss the role of VEGF in physiological angiogenesis as well as its role in non-angiogenic processes that take place in adult organs.