Enhancement Of Vascular Permeability Research Articles

The immunopathology of coronary microembolization and the underlying inflammopathophysiological mechanisms.

In coronary microembolization, inflammatory cell infiltration, patchy necrosis, and extensive intra-myocardial hemorrhage are dominant, which induce myocardial dysfunction with clinical symptoms of chronic ischemic cardiomyopathy. Microembolization can lead to obstruction of the coronary microvessels and result in the micro-infarction of the heart. The inflammation and elevated expression of the tumor necrosis factor in cardiomyocytes and the activation of extracellular ERK are involved in initiating the inflammatory response mechanism. The PI3K/Akt signaling pathway is the enriched pathway, and for controlling, inhibition of PI3K/Akt is necessary. Furthermore, the release of cytokines and the activation of inflammasomes contribute to the enhancement of vascular permeability, which results in edema within the myocardium. The immune response and inflammation represent the primary triggers in this process. The ability to control immune response and inflammation reactions may lead to the development of new therapies for microembolization.

Association of VEGFA polymorphisms with the risk of oesophageal cancer in Punjab, India: A case-control study.

Background & objectives Vascular endothelial growth factor (VEGF) is one of the most important angiogenic factors which stimulates tumour progression induction of endothelial cell migration and division, inhibition of the apoptosis of endothelial cells, induction of serine protease activity and enhancement of vascular permeability. This study aimed to investigate the correlation of VEGF+405G/C,-7C/T and+936C/T polymorphisms with oesophageal cancer risk. Methods DNA samples of 464 subjects (231 sporadic oesophageal cancer affected individuals and 233 controls) were genotyped forVEGF+936C/T,+405G/C and-7C/T polymorphisms. VEGF+936C/T and +405G/C polymorphisms were genotyped by PCR-RFLP method whereas VEGF-7C/T polymorphism was genotyped using Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Results CT genotype of VEGF-7C/T polymorphism was significantly associated with reduced risk of oesophageal cancer. VEGF-7C/T polymorphism was significantly associated with reduced risk of oesophageal cancer underdominant, co-dominant, over dominant and log-additive genetic models in total patients and in the female group. C+936G+405T-7 haplotype was significantly associated with decreased risk (P=0.01)of oesophageal cancer in total patients and also in the male group (P=0.02). Interpretation & conclusions In future, replication of the findings of the present study in a larger sample from different ethnic groups, along with functional analysis, may be insightful for the role of VEGFA polymorphisms in the pathogenesis of oesophageal cancer. Identification of the correlation of VEGF variants with specific therapy in oesophageal cancer may help in better selection of patients and monitoring treatment response in VEGF-therapy.

Tumour-specific activation of a tumour-blood transport improves the diagnostic accuracy of blood tumour markers in mice

The accuracy of blood-based early tumour recognition is compromised by signal production at non-tumoral sites, low amount of signal produced by small tumours, and variable tumour production. Here we examined whether tumour-specific enhancement of vascular permeability by the particular tumour homing peptide, iRGD, which carries dual function of binding to integrin receptors overexpressed in the tumour vasculature and is known to promote extravasation via neuropilin-1 receptor upon site-specific cleavage, might be useful to improve blood-based tumour detection by inducing a yet unrecognised vice versa tumour-to-blood transport. To detect an iRGD-induced tumour-to-blood transport, we examined the effect of intravenously injected iRGD on blood levels of α-fetoprotein (AFP) and autotaxin in several mouse models of hepatocellular carcinoma (HCC) or in mice with chronic liver injury without HCC, and on prostate-specific antigen (PSA) levels in mice with prostate cancer. Intravenously injected iRGD rapidly and robustly elevated the blood levels of AFP in several mouse models of HCC, but not in mice with chronic liver injury. The effect was primarily seen in mice with small tumours and normal basal blood AFP levels, was attenuated by an anti-neuropilin-1 antibody, and depended on the concentration gradient between tumour and blood. iRGD treatment was also able to increase blood levels of autotaxin in HCC mice, and of PSA in mice with prostate cancer. We conclude that iRGD induces a tumour-to-blood transport in a tumour-specific fashion that has potential of improving diagnosis of early stage cancer. Deutsche Krebshilfe, DKTK, LOEWE-Frankfurt Cancer Institute.

Enhanced Vascular Permeability by Microbubbles and Ultrasound in Drug Delivery.

Ultrasound and microbubbles, an ultrasound contrast agent, have recently increased attention to developing novel drug delivery systems. Ultrasound exposure can induce mechanical effects derived from microbubbles behaviors such as an expansion, contraction, and collapse depending on ultrasound conditions. These mechanical effects induce several biological effects, including enhancement of vascular permeability. For drug delivery, one promising approach is enhancing vascular permeability using ultrasound and microbubbles, resulting in improved drug transport to targeted tissues. This approach is applied to several tissues and drugs to cure diseases. This review describes the enhancement of vascular permeability by ultrasound and microbubbles and its therapeutic application, including our recent study. We also discuss the current situation of the field and its potential future perspectives.

Acid-responsive HPMA copolymer-bradykinin conjugate enhances tumor-targeted delivery of nanomedicine

Obstructed blood flow and erratic blood supply in the tumor region attenuate the distribution and accumulation of nanomedicines in the tumor. Therefore, improvement of these conditions is crucial for efficient drug delivery. In this study, we designed and synthesized a novel N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymer conjugate of BK, which possessed adequate systemic stability and tumor-selective action required to improve the accumulation of nanomedicines in the tumor. Levulinoyl-BK (Lev-BK) was conjugated to an HPMA-based polymer via an acid-cleavable hydrazone bond (P-BK). An acid-responsive release of Lev-BK from P-BK was observed, and P-BK alone after intradermal application showed below 10% of the BK activity, thus proving a reduction in the vascular permeability activity of BK when attached to the polymer carrier. P-BK pre-treatment improved blood flow in the tumor tissue by 1.4–1.7-fold, which was maintained for more than 4 h. In addition, P-BK pre-treatment increased the tumor accumulation of pegylated liposomal doxorubicin (PLD) by approximately 3-fold. Furthermore, P-BK pre-treatment led to superior antitumor activity of PLD and significantly improved the survival of tumor-bearing mice. The release of BK from P-BK in the acidic milieu of the tumor was a prerequisite for P-BK to exert its effect, as the vascular permeability enhancing activity of P-BK was negligible. Collectively, P-BK pre-treatment improved intratumoral blood flow and augmented tumor accumulation of nanomedicine, thereby resulting in a significant suppression of tumor growth. Therefore, these findings demonstrate that P-BK is a potential concomitant drug for improving the tumor delivery of nanomedicines.

Regulation of vascular permeability in cancer metastasis.

Enhancement of vascular permeability is indispensable for cancer metastasis. Weakened endothelial barrier function enhances vascular permeability. Circulating tumor cells moving in the microvasculature tend to invade into stromal tissue at the location where vascular permeability is enhanced. Many basic studies have identified permeability factors by using gene‐modified animals and cells. These factors directly/indirectly interact with endothelial cells. Here, we review vascular permeability factors and their molecular mechanisms. Interactions between tumor cells and endothelial cells are also discussed in the process of extravasation, one of the most critical steps in tumor metastasis. In some cases, primary tumors can manipulate permeability in a remote organ by secreting permeability factors. In addition, the importance of glycocalyx, which covers the endothelial cell surface, in controlling vascular permeability and tumor metastasis is also described. Furthermore, analysis of the hyperpermeable region found in a mouse model study is introduced. It clearly showed that tumor‐bearing mouse lungs had a hyperpermeable region due to the influence of a remote primary tumor, and fibrinogen deposition was observed in that region. Given that fibrinogen was reported to be a permeability factor and a key regulator of inflammation, eliminating fibrinogen deposition may prevent future metastasis.

Hirudin prevents vascular endothelial cell apoptosis and permeability enhancement induced by the serum from rat with chronic renal failure through inhibiting RhoA/ROCK signaling pathway.

Endothelial cells injury and activation contribute to arteriovenous fistula (AVF) stenosis. Hirudin (Hiru) can inhibit the activity of thrombin, which was reported to enhance endothelial cell permeability and promote vascular inflammatory responses. RhoA/ROCK signaling pathway is also important in regulating vascular endothelial permeability. This study aimed to investigate the role of Hiru on the viability and permeability of human umbilical vein endothelial cells (HUVECs) following stimulation of serum from rat with chronic renal failure (CRF) and illustrated the effects of Hiru on RhoA/ROCK signaling. Wistar rats were randomly divided into control group and CRF group. Serum from each group was collected to stimulate HUVECs. Proliferation capability was estimated with Cell Count Kit-8 (CCK-8) assay. Transwell assay was performed to determine permeability. Cell apoptosis was examined using Tunel staining. Telomere length and telomerase activity were determined by qPCR. Moreover, the expression of RhoA, ROCK1 and ROCK2 was estimated via western blot. Results showed that the serum from CRF rat significantly inhibited cell viability while enhanced cell permeability and apoptosis. Different concentrations of Hiru prevented the above effects caused by CRF serum. Additionally, Hiru recovered the CRF serum-induced decreased telomere length and telomerase activity. Hiru also inhibited the protein expression of RhoA, ROCK1 and ROCK2, which were activated by CRF serum. Moreover, the ROCK inhibitor, Y27632, exhibited similar effects with Hiru. In conclusion, Hiru-restored HUVECs cell viability, telomere length and telomerase activity, suppressed permeability and apoptosis in the presence of CRF serum might depend on inactivating the RhoA/ROCK signaling.

Eucalyptus oil reduces allergic reactions and suppresses mast cell degranulation by downregulating IgE-Fc\u03b5RI signalling

Eucalyptus oil has been used since ancient times for its bactericidal, anti-inflammatory, analgesic and sedative effects. In recent years, the action of Eucalyptus oil has been scientifically proven, and there have been reports that Eucalyptus oil suppresses the production of chemokines, cytokines and lipid mediators in basophils, alveolar macrophages and monocytes. Based on this information, we aimed to verify whether Eucalyptus oil can be used for allergic dermatitis, the incidence of which has been increasing among human skin diseases. This effect was verified using a mouse IgE-mediated local allergic model. In conclusion, topical application of Eucalyptus oil suppressed oedema and vascular permeability enhancement due to IgE-mediated allergic on the skin. In addition, we also verified the degranuration of mast cells, which is a part of its action, and examined whether 1,8-cineole, which is the main component of Eucalyptus oil, suppresses the phosphorylation of PLCγ and p38 directly or indirectly. 1,8-cineole was found to suppress degranulation of mast cells.

LCRF-0006, a small molecule mimetic of the N-cadherin antagonist peptide ADH-1, synergistically increases multiple myeloma response to bortezomib.

N‐cadherin is a homophilic cell‐cell adhesion molecule that plays a critical role in maintaining vascular stability and modulating endothelial barrier permeability. Pre‐clinical studies have shown that the N‐cadherin antagonist peptide, ADH‐1, increases the permeability of tumor‐associated vasculature thereby increasing anti‐cancer drug delivery to tumors and enhancing tumor response. Small molecule library screens have identified a novel compound, LCRF‐0006, that is a mimetic of the classical cadherin His‐Ala‐Val sequence‐containing region of ADH‐1. Here, we evaluated the vascular permeability‐enhancing and anti‐cancer properties of LCRF‐0006 using in vitro vascular disruption and cell apoptosis assays, and a well‐established pre‐clinical model (C57BL/KaLwRij/5TGM1) of the hematological cancer multiple myeloma (MM). We found that LCRF‐0006 disrupted endothelial cell junctions in a rapid, transient and reversible manner, and increased vascular permeability in vitro and at sites of MM tumor in vivo. Notably, LCRF‐0006 synergistically increased the in vivo anti‐MM tumor response to low‐dose bortezomib, a frontline anti‐MM agent, leading to regression of disease in 100% of mice. Moreover, LCRF‐0006 and bortezomib synergistically induced 5TGM1 MM tumor cell apoptosis in vitro. Our findings demonstrate the potential clinical utility of LCRF‐0006 to significantly increase bortezomib effectiveness and enhance the depth of tumor response in patients with MM.

Local Overheating of Biotissue Labeled With Upconversion Nanoparticles Under Yb3+ Resonance Excitation.

Local overheating of biotissue is a critical step for biomedical applications, such as photothermal therapy, enhancement of vascular permeability, remote control of drug release, and so on. Overheating of biological tissue when exposed to light is usually realized by utilizing the materials with a high-absorption cross section (gold, silica, carbon nanoparticles, etc.). Here, we demonstrate core/shell NaYF4:Yb3+, Tm3+/NaYF4 upconversion nanoparticles (UCNPs) commonly used for bioimaging as promising near-infrared (NIR) absorbers for local overheating of biotissue. We assume that achievable temperature of tissue labeled with nanoparticles is high enough because of Yb3+ resonance absorption of NIR radiation, whereas the use of auxiliary light-absorbing materials or shells is optional for photothermal therapy. For this purpose, a computational model of tissue heating based on the energy balance equations was developed and verified with the experimentally obtained thermal-graphic maps of a mouse in response to the 975-nm laser irradiation. Labeling of biotissue with UCNPs was found to increase the local temperature up to 2°C compared to that of the non-labeled area under the laser intensity lower than 1 W/cm2. The cellular response to the UCNP-initiated hyperthermia at subcritical ablation temperatures (lower than 42°C) was demonstrated by measuring the heat shock protein overexpression. This indicates that the absorption cross section of Yb3+ in UCNPs is relatively large, and microscopic temperature of nanoparticles exceeds the integral tissue temperature. In summary, a new approach based on the use of UCNP without any additional NIR absorbers was used to demonstrate a simple approach in the development of photoluminescent probes for simultaneous bioimaging and local hyperthermia.

Oxidative Stress, Neutrophil Elastase and Vascular Endothelial Growth Factor in Obese Pregnant Women with Preeclampsia

Oxidative stress, inflammation, and vascular endothelial proliferation and obesity are risk factors associated with preeclampsia (PE). Thepresent study aimed to investigate the levels of malondialdehyde (MDA) as a putative circulatory marker of oxidative stress, neutrophil Elastase (NE) as inflammatory marker andvascular endothelial growth factor (VEGF) as marker for vascular permeability-enhancing activities inobese women withpreeclampsia PE and compare withnormal pregnancy women. The study was carried out on 50 pregnant obese women with PE and 50 normal pregnant women. The preeclampsia women were characterized with high blood pressure 160/110 mmHg and proteinuria. The gestational age ranged from ≥32 weeks to <37 weeks. Pre pregnancyweightwas recorded. Body mass index (BMI) was calculatedat delivery.SerumMDA, NEand VEGF were estimatedby ELISA. Significant higher levels of serum MAD,NE and VEGF were observed in obese PE patients as compared to normal controls. Our results suggested thatobesity;oxidative stress, NEandVEGFbiomarkers are risk factors for PE,emphasizing their role as feasible candidate risk markersfor cases withhigh blood pressure in early pregnancy.

Optimization of Dexamethasone Administration for Maintaining Global Transduction Efficacy of Adeno-Associated Virus Serotype 9.

Glucocorticoids have been commonly used in clinic for their anti-inflammatory and immunosuppressive effects, and it has been proposed that they be used to prevent liver toxicity when systemic administration of adeno-associated virus (AAV) vectors is needed in patients with central nervous system diseases and muscular disorders. Glucocorticoids also enable modulation of vascular permeability. First, this study investigated the impact of dexamethasone on AAV vascular permeability after systemic injection. When a low dose of AAV9 was injected into mice treated with dexamethasone, global transduction and vector biodistribution were not significantly different in most tissues, other than the liver and the heart, when compared to control mice. When AAV9 vectors were used at a high dose, both the transgene expression and the AAV vector genome copy number were significantly decreased in the majority of murine tissues. However, no effect on global transduction was observed when dexamethasone was administered 2 h after AAV vector injection. The study on the kinetics of AAV virus clearance demonstrated that dexamethasone slowed down the clearance of AAV9 in the blood after systemic application. The mechanism study showed that dexamethasone inhibited the enhancement of AAV9 vascular permeability mediated by serum proteins. The findings indicate that dexamethasone is able to inhibit the vascular permeability of AAV and compromise the therapeutic effect after systemic administration of AAV vector. In conclusion, this study provides valuable information for the design of future clinical studies when glucocorticoids are needed to be compatible with the systemic administration of AAV vectors in patients with central nervous system and muscular diseases.

Fasting-dependent Vascular Permeability Enhancement in Brown Adipose Tissues Evidenced by Using Carbon Nanotubes as Fluorescent Probes

Brown adipose tissue (BAT), which is composed of thermogenic brown adipocytes (BA) and non-parenchymal components including vasculatures and extracellular matrix, contribute to the maintenance of body temperature. BAT distribution is detected by positron emission tomography-computed tomography (PET/CT) using 18F-fluorodeoxy glucose (18F-FDG) or single-photon-emission computed tomography-computed tomography (SPECT/CT) using [123/125I]-beta-methyl-p-iodophenyl-pentadecanoic acid. Although sympathetic nerve activity and thermogenic capacity of BA is downregulated under fasting conditions in mice, fasting-dependent structural changes and fluid kinetics of BAT remain unknown. Here we show that the fasting induces fine and reversible structural changes in the non-parenchymal region in murine BAT with widened intercellular spaces and deformed collagen bands as revealed by electron microscopy. Interestingly, a newly introduced near infrared fluorescent probe of single-walled carbon nanotubes (CNTs) coated with phospholipid polyethylene glycol (PLPEG) easily demonstrated enhanced vascular permeability in BAT by the fasting. PLPEG-CNTs extravasated and remained in intercellular spaces or further redistributed in parenchymal cells in fasted mice, which is a previously unknown phenomenon. Thus, PLPEG-CNTs provide a powerful tool to trace fluid kinetics in sub-tissue levels.

Assessment of circulating vascular endothelial growth factor in patients with stable and exacerbated chronic obstructive pulmonary disease

Objective This study aimed to evaluate the diagnostic value of serum vascular endothelial growth factor (VEGF) assessment during stable and acute exacerbations of chronic obstructive pulmonary disease (COPD). Background VEGF is a cytokine that has potent angiogenic and vascular permeability-enhancing activities. VEGF serum level was found to increase in a number of inflammatory disorders. Patient and methods This study was carried out in the Chest and Medical Biochemistry Departments, Faculty of Medicine, Menoufia University and El-Mahalla Chest Hospital in the period from July 2015 to March 2016. It included 75 patients, with a mean age of 54.7 ± 7.55 years. The patients were subjected to clinical examination and standard spirometric measures including percentage of predicted forced vital capacity, percentage of predicted forced expiratory volume in the first second, and forced expiratory volume in the first second/forced vital capacity ratio. Measurement of VEGF serum levels was done in patients with acute exacerbations of COPD on the first day of hospitalization, whereas for patients with stable COPD and for the healthy controls, the sample was taken on the same day of the spirometric maneuver. Results VEGF level was significantly elevated in patients with stable chronic obstructive pulmonary disease (COPD) compared with controls and also was significantly higher in patients with acute exacerbations of COPD compared with patients with stable COPD. Conclusion VEGF is significantly elevated in patients with acute exacerbations of COPD and is proportional to the severity of stable COPD. Therefore, it can be used as a biomarker for COPD.

A novel mechanism of neovascularization in peritoneal dissemination via cancer-associated mesothelial cells affected by TGF-β derived from ovarian cancer.

Epithelial ovarian cancer (EOC) is believed to cause peritoneum dissemination through microenvironmental cell‑to-cell communication between the tumor and mesothelium, leading to the further acquisition of progressive and metastatic potentials. In the present study, we aimed to determine the role of cancer-associated mesothelial cells (CAMCs) in the promotion of tumor neovascularization and vascular permeability via enhanced vascular endothelial growth factor (VEGF) production. We examined whether a characteristic morphological change in human peritoneal mesothelial cells (HPMCs) was observed in the presence of malignant ascites and tumor-derived TGF-β. We focused on the enhanced production of VEGF in CAMCs and its crucial role in endothelial migration and tube formation. Normal HPMCs showed an epithelial morphology with a cobblestone appearance. When HPMCs were co-cultured with malignant ascites from patients with advanced EOC, a dramatic morphologic change was noted from an epithelioid pattern to an α-SMA-positive fibroblastic, mesenchymal pattern. Additionally, we found that EOC-derived TGF-β induced typical EMT-like morphological alteration in HPMCs, which was associated with CAMCs. We further discovered that CAMCs play a crucial role in the enhanced migration and tube formation of endothelial cells by the promotion of VEGF production. In conclusion, our findings indicate the possible involvement of CAMCs in the neovascularization of EOC and enhancement of vascular permeability, resulting in the formation of malignant ascites. The novel mechanism of CAMCs as a facilitator of EOC progression is displayed by microenvironmental cell-to-cell communication between EOC and the mesothelium.

19P - An endothelial premetastatic-like niche is promoted by tumor-secreted factors derived from highly metastatic breast cancer cells in vitro

Background: It is well established that primary tumour can modify secondary organs long before the circulating tumor cells reach their metastatic targets. These modifications are mainly exerted through tumor-secreted factors and can act on several cell types to form what is called the pre-metastatic niche. Pre-metastatic endothelial niche play a key role in the extravasation process during metastasis. Here we describe the effect of the mixture of secreted factors by tumor cells over endothelial changes that facilitates tumor cell transendothelial migration. Methods: Adhesion assay Human umbilical vein endothelial cells (HUVEC) cells were stimulated or not with TNF-α [10ng/ml] or Tumor Secreted Factors (TSFs) [10 µg/ml] from MDA-MB-231 or MCF-7 cell lines. HUVEC monolayers were co-cultured with a U937(3H) cells. After 3h firm attached U937(3H) were lysed and radioactivity was measured. Vascular permeability assay HUVEC monolayers were cultured in Boyden chambers. Cells were stimulated or not with TNF-α [10ng/ml] or TSFs [10 µg/ml] and incubated for 12h. Afterwards a dextran-FITC solution was added for 20 min and the bottom well fluorescence was quantified. Transendothelial migration assay HUVEC monolayers were cultured in Boyden chambers. Cells were stimulated or not with TNF-α [10ng/ml] or TSFs [10 µg/ml] and incubated for 10h. Fluorescent labeled MDA-MB-231 cell suspension 2x104 was added (24h) and the migrant cells were counted under an epifluorescence microscope. Results: Adhesion assay revealed that HUVEC stimulated with MDA-231 TSFs attached U937 cells 6-fold comparing to the MCF-7 TSFs or control, in a similar way as TNF-α did. The MDA-TSFs were able to increase the HUVEC monolayer permeability exceeded about 30% of the TNF-α induced permeability. A 1.5-fold increase of transendothelial migration cells was observed in HUVEC stimulated with MDA-MB-231 TSFs. Conclusions: Tumor secreted factors derived from highly metastatic cell line MDA-MB-231 are capable to induce a premetastatic-like endothelial state, increasing the tumor cell transendothelial migration, adhesion to the HUVEC monolayer as well as vascular permeability enhancement. Clinical trial identification: 11-62-2014 Legal entity responsible for the study: Instituto de Investigaciones Biomédicas, UNAM Funding: Programa de Doctorado en Ciencias Biomédicas, Universidad Nacional Autónoma de México (UNAM), fellowship 509589 from CONACYT. Disclosure: All authors have declared no conflicts of interest.

Morphologic mechanisms of increased vascular permeability of triolein emulsion to the blood-brain barrier.

Triolein emulsion has been known to increase vascular permeability in the brain when it is infused into the carotid artery. The purpose of this study was to identify the morphologic mechanism of increased vascular permeability in brain induced by infusion of emulsified triolein into the carotid artery by transmission electron microscopy (TEM). Triolein emulsion was infused into the carotid artery of rats. TEM using lanthanum tracer was used to evaluate morphologic changes in endothelium with a focus on transcytotic vesicles and tight junction opening. The treat group showed multiple transcytotic vesicles containing lanthanum tracer within endothelium on TEM. TEM also revealed that lanthanum tracer entered neural interstitium through tight junctions between capillary endothelial cells infrequently in the treat group. No evidence of transcytotic vesicles containing lanthanum tracer or lanthanum leakage through tight junctions was observed in the control group. Transcytosis and the opening of tight junctions appears the pathway for vascular permeability enhancement by triolein. This result could be utilized in studies on the blood-brain barrier and by those searching for chemotherapeutic methods that deliver anti-tumor agents to normally drug inaccessible organs.

Degradation of bradykinin by a metalloendopeptidase from Streptococcus pyogenes

ObjectivesStreptococcus pyogenes secretes streptococcal pyrogenic exotoxin B (SpeB), which cleaves kininogen to liberate bradykinin. In addition, this bacterium also has cell-associated bradykinin-degrading activity. Here, we characterized the bradykinin-degrading enzyme produced by S. pyogenes. MethodsThe effects of various peptidase inhibitors on bradykinin degradation by intact S. pyogenes and cell lysates were assessed. Cleavage of bradykinin and other peptides by a recombinant putative metalloendopeptidase (Sp-Pep) from S. pyogenes was analyzed by mass spectrometry. The enhancement of vascular permeability induced by bradykinin (before and after treatment with Sp-Pep) was evaluated in guinea pig skin. ResultsVarious S. pyogenes strains expressed Sp-Pep. Immunoadsorption of S. pyogenes with an anti-Sp-Pep antibody showed that 80% of the bradykinin-degrading activity in S. pyogenes was due to Sp-Pep. Recombinant Sp-Pep cleaved bradykinin, and cleavage caused a loss of its extravasation-inducing potential. Sp-Pep-mediated degradation of bradykinin was 40 times more efficient than degradation of substance P and angiotensin II. While S. pyogenes secreted mature SpeB in stationary phase, this bacterium produced Sp-Pep during all tested growth phases. ConclusionsS. pyogenes produces a cell-associated metalloendopeptidase that degrades bradykinin.

Increased microvascular permeability in mice lacking Epac1 (Rapgef3).

AimMaintenance of the blood and extracellular volume requires tight control of endothelial macromolecule permeability, which is regulated by cAMP signalling. This study probes the role of the cAMP mediators rap guanine nucleotide exchange factor 3 and 4 (Epac1 and Epac2) for in vivo control of microvascular macromolecule permeability under basal conditions.MethodsEpac1−/− and Epac2−/− C57BL /6J mice were produced and compared with wild‐type mice for transvascular flux of radio‐labelled albumin in skin, adipose tissue, intestine, heart and skeletal muscle. The transvascular leakage was also studied by dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) using the MRI contrast agent Gadomer‐17 as probe.ResultsEpac1−/− mice had constitutively increased transvascular macromolecule transport, indicating Epac1‐dependent restriction of baseline permeability. In addition, Epac1−/− mice showed little or no enhancement of vascular permeability in response to atrial natriuretic peptide (ANP), whether probed with labelled albumin or Gadomer‐17. Epac2−/− and wild‐type mice had similar basal and ANP‐stimulated clearances. Ultrastructure analysis revealed that Epac1−/− microvascular interendothelial junctions had constitutively less junctional complex.ConclusionEpac1 exerts a tonic inhibition of in vivo basal microvascular permeability. The loss of this tonic action increases baseline permeability, presumably by reducing the interendothelial permeability resistance. Part of the action of ANP to increase permeability in wild‐type microvessels may involve inhibition of the basal Epac1‐dependent activity.

Monitoring vascular permeability and remodeling after endothelial injury in a murine model using a magnetic resonance albumin-binding contrast agent.

Despite the beneficial effects of vascular interventions, these procedures may damage the endothelium leading to increased vascular permeability and remodeling. Re-endothelialization of the vessel wall, with functionally and structurally intact cells, is controlled by endothelial nitric oxide synthase (NOS3) and is crucial for attenuating adverse effects after injury. We investigated the applicability of the albumin-binding MR contrast agent, gadofosveset, to noninvasively monitor focal changes in vascular permeability and remodeling, after injury, in NOS3-knockout (NOS3(-/-)) and wild-type (WT) mice in vivo. WT and NOS3(-/-) mice were imaged at 7, 15, and 30 days after aortic denudation or sham-surgery. T1 mapping (R1=1/T1, s(-1)) and delayed-enhanced MRI were used as measurements of vascular permeability (R1) and remodeling (vessel wall enhancement, mm(2)) after gadofosveset injection, respectively. Denudation resulted in higher vascular permeability and vessel wall enhancement 7 days after injury in both strains compared with sham-operated animals. However, impaired re-endothelialization and increased neovascularization in NOS3(-/-) mice resulted in significantly higher R1 at 15 and 30 days post injury compared with WT mice that showed re-endothelialization and lack of neovascularization (R1 [s(-1)]=15 days: NOS3 (-/-)4.02 [interquartile range, IQR, 3.77-4.41] versus WT2.39 [IQR, 2.35-2.92]; 30 days: NOS3 (-/-)4.23 [IQR, 3.94-4.68] versus WT2.64 [IQR, 2.33-2.80]). Similarly, vessel wall enhancement was higher in NOS3(-/-) but recovered in WT mice (area [mm(2)]=15 days: NOS3 (-/-)5.20 [IQR, 4.68-6.80] versus WT2.13 [IQR, 0.97-3.31]; 30 days: NOS3 (-/-)7.35 [IQR, 5.66-8.61] versus WT1.60 [IQR, 1.40-3.18]). Ex vivo histological studies corroborated the MRI findings. We demonstrate that increased vascular permeability and remodeling, after injury, can be assessed noninvasively using an albumin-binding MR contrast agent and may be used as surrogate markers for evaluating the healing response of the vessel wall after injury.