Alterations In Vascular Permeability Research Articles

Amyloid-β (Aβ) immunotherapy induced microhemorrhages are associated with activated perivascular macrophages and peripheral monocyte recruitment in Alzheimer’s disease mice

BackgroundAmyloid-related imaging abnormalities (ARIA) have been identified as the most common and serious adverse events resulting from pathological changes in the cerebral vasculature during several recent anti-amyloid-β (Aβ) immunotherapy trials. However, the precise cellular and molecular mechanisms underlying how amyloid immunotherapy enhances cerebral amyloid angiopathy (CAA)-mediated alterations in vascular permeability and microhemorrhages are not currently understood. Interestingly, brain perivascular macrophages have been implicated in regulating CAA deposition and cerebrovascular function however, further investigations are required to understand how perivascular macrophages play a role in enhancing CAA-related vascular permeability and microhemorrhages associated with amyloid immunotherapy.MethodsIn this study, we examined immune responses induced by amyloid-targeting antibodies and CAA-induced microhemorrhages using histology and gene expression analyses in Alzheimer’s disease (AD) mouse models and primary culture systems.ResultsIn the present study, we demonstrate that anti-Aβ (3D6) immunotherapy leads to the formation of an antibody immune complex with vascular amyloid deposits and induces the activation of CD169+ perivascular macrophages. We show that macrophages activated by antibody mediated Fc receptor signaling have increased expression of inflammatory signaling and extracellular matrix remodeling genes such as Timp1 and MMP9 in vitro and confirm these key findings in vivo. Finally, we demonstrate enhanced vascular permeability of plasma proteins and recruitment of inflammatory monocytes around vascular amyloid deposits, which are associated with hemosiderin deposits from cerebral microhemorrhages, suggesting the multidimensional roles of activated perivascular macrophages in response to Aβ immunotherapy.ConclusionsIn summary, our study establishes a connection between Aβ antibodies engaged at CAA deposits, the activation of perivascular macrophages, and the upregulation of genes involved in vascular permeability. However, the implications of this phenomenon on the susceptibility to microhemorrhages remain to be fully elucidated. Further investigations are warranted to determine the precise role of CD169 + perivascular macrophages in enhancing CAA-mediated vascular permeability, extravasation of plasma proteins, and infiltration of immune cells associated with microhemorrhages.

Exploring the Potential of Therapeutic Agents Targeted towards Mitigating the Events Associated with Amyloid-β Cascade in Alzheimer's Disease.

One of the most commonly occurring neurodegenerative disorders, Alzheimer’s disease (AD), encompasses the loss of cognitive and memory potential, impaired learning, dementia and behavioral defects, and has been prevalent since the 1900s. The accelerating occurrence of AD is expected to reach 65.7 million by 2030. The disease results in neural atrophy and disrupted inter-neuronal connections. Amongst multiple AD pathogenesis hypotheses, the amyloid beta (Aβ) cascade is the most relevant and accepted form of the hypothesis, which suggests that Aβ monomers are formed as a result of the cleavage of amyloid precursor protein (APP), followed by the conversion of these monomers to toxic oligomers, which in turn develop β-sheets, fibrils and plaques. The review targets the events in the amyloid hypothesis and elaborates suitable therapeutic agents that function by hindering the steps of plaque formation and lowering Aβ levels in the brain. The authors discuss treatment possibilities, including the inhibition of β- and γ-secretase-mediated enzymatic cleavage of APP, the immune response generating active immunotherapy and passive immunotherapeutic approaches targeting monoclonal antibodies towards Aβ aggregates, the removal of amyloid aggregates by the activation of enzymatic pathways or the regulation of Aβ circulation, glucagon-like peptide-1 (GLP-1)-mediated curbed accumulation and the neurotoxic potential of Aβ aggregates, bapineuzumab-mediated vascular permeability alterations, statin-mediated Aβ peptide degradation, the potential role of ibuprofen and the significance of natural drugs and dyes in hindering the amyloid cascade events. Thus, the authors aim to highlight the treatment perspective, targeting the amyloid hypothesis, while simultaneously emphasizing the need to conduct further investigations, in order to provide an opportunity to neurologists to develop novel and reliable treatment therapies for the retardation of AD progression.

Brain Endothelium: The "Innate Immunity Response Hypothesis" in Cerebral Malaria Pathogenesis.

Cerebral malaria (CM) is a life-threatening neurological syndrome caused by Plasmodium falciparum infection afflicting mainly children in Africa. Current pathogenesis models implicate parasite and host-derived factors in impairing brain vascular endothelium (BVE) integrity. Sequestration of Plasmodium-infected red blood cells (iRBCs) in brain microvessels is a hallmark of CM pathology. However, the precise mechanisms driving loss of blood-brain barrier (BBB) function with consequent brain injury are still unsettled and it is plausible that distinct pathophysiology trajectories are involved. Studies in humans and in the mouse model of CM indicate that inflammatory reactions intertwined with microcirculatory and coagulation disturbances induce alterations in vascular permeability and impair BBB integrity. Yet, the role of BVE as initiator of immune responses against parasite molecules and iRBCs is largely unexplored. Brain endothelial cells express pattern recognition receptors (PRR) and are privileged sensors of blood-borne infections. Here, we focus on the hypothesis that innate responses initiated by BVE and subsequent interactions with immune cells are critical to trigger local effector immune functions and induce BBB damage. Uncovering mechanisms of BVE involvement in sensing Plasmodium infection, recruiting of immune cells and directing immune effector functions could reveal pharmacological targets to promote BBB protection with potential applications in CM clinical management.

Permeability changes and effect of chemotherapy in brain adjacent to tumor in an experimental model of metastatic brain tumor from breast cancer

BackgroundBrain tumor vasculature can be significantly compromised and leakier than that of normal brain blood vessels. Little is known if there are vascular permeability alterations in the brain adjacent to tumor (BAT). Changes in BAT permeability may also lead to increased drug permeation in the BAT, which may exert toxicity on cells of the central nervous system. Herein, we studied permeation changes in BAT using quantitative fluorescent microscopy and autoradiography, while the effect of chemotherapy within the BAT region was determined by staining for activated astrocytes.MethodsHuman metastatic breast cancer cells (MDA-MB-231Br) were injected into left ventricle of female NuNu mice. Metastases were allowed to grow for 28 days, after which animals were injected fluorescent tracers Texas Red (625 Da) or Texas Red dextran (3 kDa) or a chemotherapeutic agent 14C-paclitaxel. The accumulation of tracers and 14C-paclitaxel in BAT were determined by using quantitative fluorescent microscopy and autoradiography respectively. The effect of chemotherapy in BAT was determined by staining for activated astrocytes.ResultsThe mean permeability of texas Red (625 Da) within BAT region increased 1.0 to 2.5-fold when compared to normal brain, whereas, Texas Red dextran (3 kDa) demonstrated mean permeability increase ranging from 1.0 to 1.8-fold compared to normal brain. The Kin values in the BAT for both Texas Red (625 Da) and Texas Red dextran (3 kDa) were found to be 4.32 ± 0.2 × 105 mL/s/g and 1.6 ± 1.4 × 105 mL/s/g respectively and found to be significantly higher than the normal brain. We also found that there is significant increase in accumulation of 14C-Paclitaxel in BAT compared to the normal brain. We also observed animals treated with chemotherapy (paclitaxel (10 mg/kg), erubilin (1.5 mg/kg) and docetaxel (10 mg/kg)) showed activated astrocytes in BAT.ConclusionsOur data showed increased permeation of fluorescent tracers and 14C-paclitaxel in the BAT. This increased permeation lead to elevated levels of activated astrocytes in BAT region in the animals treated with chemotherapy.

Mast cells in the brain- Old cells, new target.

Mast cells (MCs) are mainly known for their involvement on allergic reactions through degranulation and release of vasoactive, inflammatory and nociceptive mediators. Upon encountering an allergen, MCs are first responders, true sensors of the environment, actually they respond to a wide range of "danger" signals both immunological and non-immunological in rapid and selective manner. They secrete both preformed and newly synthesized mediators acting as effectors in relationship between nervous, vascular and immune systems. For this peculiarity, MCs are "master regulators" and key players of the immune system as well as important source of essential and beneficial mediators with crucial roles in the regulation of various physiological processes. MCs are unique cells with multiple capabilities. It has well known that MCs are critical for the pathogenesis of inflammatory disease. MCs exert their effect through alteration of vascular permeability and recruitment of inflammatory cells. While a functional involvement of peripheral MCs in inflammatory conditions is well established, the role of Central Nervous System MCs is not well understood yet. Increasing evidence indicate that in the brain, the inflammation is strongly involved in the pathogenesis of neurodegenerative and neuropsychiatric diseases. In this review, we discuss some aspects of the current knowledge of MCs role in the brain and their potential role as therapeutic emerging target for neural diseases.

Glycocalyx and sepsis-induced alterations in vascular permeability.

Endothelial cells line the inner portion of the heart, blood vessels, and lymphatic vessels; a basal membrane of extracellular matrix lines the extraluminal side of endothelial cells. The apical side of endothelial cells is the site for the glycocalyx, which is a complex network of macromolecules, including cell-bound proteoglycans and sialoproteins. Sepsis-associated alterations of this structure may compromise endothelial permeability with associated interstitial fluid shift and generalized edema. Indeed, in sepsis, the glycocalyx acts as a target for inflammatory mediators and leukocytes, and its ubiquitous nature explains the damage of tissues that occurs distant from the original site of infection. Inflammatory-mediated injury to glycocalyx can be responsible for a number of specific clinical effects of sepsis, including acute kidney injury, respiratory failure, and hepatic dysfunction. Moreover, some markers of glycocalyx degradation, such as circulating levels of syndecan or selectins, may be used as markers of endothelial dysfunction and sepsis severity. Although a great deal of experimental evidence shows that alteration of glycocalyx is widely involved in endothelial damage caused by sepsis, therapeutic strategies aiming at preserving its integrity did not significantly improve the outcome of these patients.

Nitric Oxide Increases Arterial Endotheial Permeability through Mediating VE-Cadherin Expression during Arteriogenesis.

Macrophage invasion is an important event during arteriogenesis, but the underlying mechanism is still only partially understood. The present study tested the hypothesis that nitric oxide (NO) and VE-cadherin, two key mediators for vascular permeability, contribute to this event in a rat ischemic hindlimb model. In addition, the effect of NO on expression of VE-caherin and endothelial permeability was also studied in cultured HUVECs. We found that: 1) in normal arteriolar vessels (NAV), eNOS was moderately expressed in endothelial cells (EC) and iNOS was rarely detected. In contrast, in collateral vessels (CVs) induced by simple femoral artery ligation, both eNOS and iNOS were significantly upregulated (P<0.05). Induced iNOS was found mainly in smooth muscle cells, but also in other vascular cells and macrophages; 2) in NAV VE-cadherin was strongly expressed in EC. In CVs, VE-cadherin was significantly downregulated, with a discontinuous and punctate pattern. Administration of nitric oxide donor DETA NONOate (NONOate) further reduced the amounts of Ve-cadherin in CVs, whereas NO synthase inhibitor L-NAME inhibited downregulation of VE-cadherin in CVs; 3) in normal rats Evans blue extravasation (EBE) was low in the musculus gracilis, FITC-dextron leakage was not detected in the vascular wall and few macrophages were observed in perivascular space. In contrast, EBE was significantly increased in femoral artery ligation rats, FITC-dextron leakage and increased amounts of macrophages were detected in CVs, which were further enhanced by administration of NONOate, but inhibited by L-NAME supplement; 4) in vitro experiments confirmed that an increase in NO production reduced VE-cadherin expression, correlated with increases in the permeability of HUVECs. In conclusion, our data for the first time reveal the expression profile of VE-cadherin and alterations of vascular permeability in CVs, suggesting that NO-mediated VE-cadherin pathway may be one important mechanism responsible, at least in part, for macrophage invasion during arteriogenesis.

First report of the characterization of the pathophysiological mechanisms caused by the freshwater catfish Pimelodus maculatus (order: Siluriformes).

Injuries caused by aquatic animals in Brazil in most cases are provoked by marine and freshwater catfish. Pimelodus maculatus is a freshwater catfish very common in Brazilian basins that causes frequent accidents mainly amongst fishermen, and whose venom characteristics and pathological mechanisms of the venom are poorly known. In the present study for the first time, we have characterized the main pathophysiological mechanisms associated with the clinical manifestation (pain, local inflammation and edema) of the envenomations caused by P. maculatus crude venom. It was estimated that the crude venom of one P. maculatus stinger contains approximately 100μg of protein, likely the quantity involved in the envenomation. P. maculatus crude venom induced marked nociceptive and edematogenic effects and caused vascular permeability alterations at doses from 30 to 100μg/animal. Additionally, P. maculatus crude venom caused a decrease in the contraction force in in situ frog heart, did not cause hemorrhage or alterations in clotting times (prothrombin time and activated partial thromboplastin time), but induced significant changes in the levels of CK and its isoenzyme CK-MB in mice. In the present work, we present a correlation between the effects obtained experimentally and the main symptoms observed in the human accidents provoked by P.maculatus.

Clinical activity and correlative DCE-MRI imaging of G-202, a thapsigargin-based prostate-specific membrane antigen-activated prodrug, in progressive hepatocellular cancer.

301 Background: G-202 is a thapsigargin-based prodrug whose cytotoxic activity is blocked by a masking peptide that is cleaved by prostate-specific membrane antigen (PSMA), a membrane-bound protease expressed in prostate cancer and the endothelium of tumor vasculature but not in most other tissues or normal tissue vasculature. In a Phase I study of G-202, prolonged disease stabilization was observed in the subset of patients with hepatocellular carcinoma (HCC) and prompted development of a Phase II study to further evaluate activity of G-202 in patients with HCC who have progressed on sorafenib. Methods: G-202 is administered by iv infusion on Days 1, 2 and 3 of a 28-day cycle; prophylactic hydration is administered with infusion to ameliorate incidence of creatinine elevations. HCC is typically highly-vascularized, and DCE-MRI is performed in consenting patients at baseline and after treatment on approximately Day 6 of Cycle 2 to evaluate possible effects of G-202 on blood flow metrics in hepatic lesions. DCE-MRI is a non-invasive method of investigating vascular structure and function and is sensitive to alterations in vascular permeability and blood flow. DCE-MRI measurements were made on 1.5 Tesla MRI and the volume transfer coefficients, Ktrans, of HCC tumor lesions were calculated using arterial input function derived from signal in abdominal aorta. Results: Among the 22 patients treated to date, G-202 related SAEs in this patient population have been creatinine increase/acute renal failure/acute kidney injury (3 pts) and congestive heart failure (1 pt). While objective responses (CR, PR) have not been observed in these patients with advanced disease, the rate of disease stabilization has been remarkable, with &gt;70% of patients exhibiting SD. In patients undergoing DCE-MRI, an average 56% decrease in Ktranshas been observed after administration of G-202. Conclusions: G-202 is generally well-tolerated and promotes disease stabilization in patients with advanced HCC who have progressed on sorafenib. DCE-MRI findings of decreased tumor Ktrans values suggests that G-202 reduces early arterial blood flow in hepatic lesions. Clinical trial information: NCT01777594.

Modulation of α-enolase post-translational modifications by dengue virus: increased secretion of the basic isoforms in infected hepatic cells.

Hepatic cells are major sites of dengue virus (DENV) replication and liver injury constitutes a characteristic of severe forms of dengue. The role of hepatic cells in dengue pathogenesis is not well established, but since hepatocytes are the major source of plasma proteins, changes in protein secretion by these cells during infection might contribute to disease progression. Previously, we showed that DENV infection alters the secretion pattern of hepatic HepG2 cells, with α-enolase appearing as one of the major proteins secreted in higher levels by infected cells. ELISA analysis demonstrated that DENV infection modulates α-enolase secretion in HepG2 cells in a dose-dependent manner, but has no effect on its gene expression and on the intracellular content of the protein as assessed by PCR and western blot analyses, respectively. Two-dimensional western blots showed that both intracellular and secreted forms of α-enolase appear as five spots, revealing α-enolase isoforms with similar molecular weights but distinct isoeletric points. Remarkably, quantification of each spot content revealed that DENV infection shifts the isoform distribution pattern of secreted α-enolase towards the basic isoforms, whereas the intracellular protein remains unaltered, suggesting that post-translational modifications might be involved in α-enolase secretion by infected cells. These findings provide new insights into the mechanisms underlying α-enolase secretion by hepatic cells and its relationship with the role of liver in dengue pathogenesis. In addition, preliminary results obtained with plasma samples from DENV-infected patients suggest an association between plasma levels of α-enolase and disease severity. Since α-enolase binds plasminogen and modulates its activation, it is plausible to speculate the association of the increase in α-enolase secretion by infected hepatic cells with the haemostatic dysfunction observed in dengue patients including the promotion of fibrinolysis and vascular permeability alterations.

Phenotypes and biomarkers of diabetic retinopathy. Personalized medicine for diabetic retinopathy: the Weisenfeld award.

Phenotypes and biomarkers of diabetic retinopathy. Personalized medicine for diabetic retinopathy: the Weisenfeld award.

Ghrelin’s effects in diabetic retinopathy: Inhibition of choroid retinal cells migration cultured under a hyperglycemic environment.

AbstractPurpose The purpose of this work is to investigate the effect of ghrelin in a primate choroid retinal cell line cultured under hyperglycemic conditions and its effect on the early changes of diabetic retinopathy in an animal model of type1 diabetes mellitus (DM1).Methods A RF/6a cell line was used in the in vitro assay. Cell migration was assessed using the wound healing assay under increasing (0‐300mM) glucose concentrations. To test its effect, ghrelin was added (10‐5‐10‐10nM) to the cell cultures for 24h. Positive controls had VEGF added to the medium. For the in vivo studies, diabetic Wistar rats received intravitreal injections of either ghrelin (81nM) or saline every 4 weeks for 3 months. Vascular permeability was assessed using the Evans blue assay.Results Increasing concentrations of glucose show a reduction in cell migration distance. We defined 10 mM of glucose as the basal and 250 mM as the hyperglycemic condition. At a concentration of 10‐8 nM ghrelin potentiates the reduction of migration induced by the hyperglycemic medium, and reduces the migration induced by VEGF. Regarding the in vivo model, diabetic animals treated with intravitreal ghrelin injections showed no alteration in vascular permeability, when compared with diabetic controls.Conclusion Ghrelin reduces cell migration in choroid‐retinal cells under hyperglycemic media, but appears to have no effect on the vascular permeability in a DM1 animal model.

High mobility group box protein 1 as a novel vascular permeability factor derived from endothelial inflammasome activation during obesity (688.5)

The early onset of type II diabetes in obese individuals is characteristic of increased vascular permeability leading to diabetic vasculopathy. However, it remains unknown how obesity instigates endothelial dysfunction resulting in vascular hyperpermeability. Here, we tested a hypothesis that visfatin, an injurious adipokine activates endothelial Nlrp3 inflammsome to produce high mobility group box protein 1 (HMGB1) and that HMGB1 serves as a novel vascular permeability factor to mediate the onset of obesity‐associated vascular hyperpermeability. In coronary arteries of Nlrp3+/+ mice fed high fat diet (HFD) for 6 weeks, confocal microscopic analysis showed significantly lower expression of gap junction proteins (GJPs) including VE‐Cadherin, ZO‐2 and occludin in the coronary arterial endothelium compared to mice on normal diet (ND). In vivo assessment of vascular integrity demonstrated that more Evans blue was extravasated into the myocardium in mice on HFD compared to mice on ND. However, such HFD‐induced decrease in endothelial GJP level and increase in vascular permeability were significantly attenuated in Nlrp3‐/‐ mice. Accompanied with these vascular permeability alterations, interestingly, HMGB1 expression was elevated in coronary arterial endothelium of HFD‐treated Nlrp3+/+ mice, but not in Nlrp3‐/‐ mice. In cultured mouse microvascular endothelial cells (MVECs), visfatin markedly decreased expression of GJPs and increased endothelial permeability. These visfatin‐induced changes in GJPs and endothelial permeability were blocked when MVECs were treated with HMGB1 inhibitor glycyrrhizin, caspase‐1 inhibitor WEHD or siRNA targeting HMGB1 receptor RAGE, respectively. Together, these data suggest that during obesity Nlrp3 inflammasome is activated due to the action of increased adipokines such as visfatin, which produces HMGB1 to serve as a vacular permeability factor leading to the onset of diabetic vasculopathy and ultimately resulting in atherosclerosis.Grant Funding Source: Supported by NIH grants HL057244, HL091464 and HL075316

Alteration of vascular permeability in burn injury

Alteration of vascular permeability in burn injury

Alteration of vascular permeability in burn injury

Massive burn trauma is characterized by hypovolemic shock induced by the loss of plasma from vessels. The elevation of vascular permeability and the ultimate formation of tissue edema are important events during the development of severe burn injury. The underlying mechanisms involved in the increased permeability include the activation of multiple endothelial signaling pathways and the changes of endothelial structure and functions. This review summarizes some of our recent discoveries in endothelial mechanisms during burninduced vascular hyper-permeability. The emphasis is put on tight junction, adherens junction, and the contraction of endothelial cells. The effects of several protein kinases, including Rho kinase, protein kinase C, and MAPKs are also stressed.

VEGF expression and microvascular responses to severe transient hypoxia in the fetal sheep brain

Fetal hypoxia contributes significantly to the pathogenesis of permanent perinatal brain injury. We hypothesized that hypoxia-induced cerebral angiogenesis and microvascular changes would occur in fetal sheep subjected to a severe hypoxic insult produced by umbilical cord occlusion (UCO) for 10 min. At 124-126 d of gestation, singleton fetal sheep underwent surgery for implantation of catheters and placement of an inflatable cuff around the umbilical cord. A 10-min UCO or sham UCO (n = 5) was induced at 130 d gestation. The fetal brain was collected at 24 h (n = 5) or 48 h (n = 4) after UCO for immunohistochemical analysis of vascular endothelial growth factor (VEGF), Ki67, and serum albumin. By 48 h after UCO, the percentage of blood vessels expressing VEGF had increased in the subventricular zone, periventricular and subcortical white matter, corpus callosum, and cortex. Alterations in vascular permeability (albumin extravasation) were observed only in the periventricular and subcortical white matter and the subventricular zone following UCO. The upregulation of VEGF expression and increased leakage of plasma protein in the fetal sheep brain show that the microvasculature in white matter is sensitive to hypoxia in the near-term brain.

Bevacizumab-Induced Alterations in Vascular Permeability and Drug Delivery: A Novel Approach to Augment Regional Chemotherapy for In-Transit Melanoma

To investigate whether the systemically administered anti-VEGF monoclonal antibody bevacizumab could improve regional chemotherapy treatment of advanced extremity melanoma by enhancing delivery and tumor uptake of regionally infused melphalan (LPAM). After treatment with systemic bevacizumab or saline, changes in vascular permeability were determined by spectrophotometric analysis of tumors infused with Evan's blue dye. Changes in vascular structure and tumor hemoglobin-oxygen saturation HbO(2) were determined by intravital microscopy and diffuse reflectance spectroscopy, respectively. Rats bearing the low-VEGF secreting DM738 and the high-VEGF secreting DM443 melanoma xenografts underwent isolated limb infusion (ILI) with melphalan (LPAM) or saline via the femoral vessels. The effect of bevacizumab on terminal drug delivery was determined by immunohistochemical analysis of LPAM-DNA adducts in tumor tissues. Single-dose bevacizumab given three days before ILI with LPAM significantly decreased vascular permeability (50.3% in DM443, P < 0.01 and 35% in DM738, P < 0.01) and interstitial fluid pressure (57% in DM443, P < 0.01 and 50% in DM738, P = 0.01). HbO(2) decreased from baseline in mice following treatment with bevacizumab. Systemic bevacizumab significantly enhanced tumor response to ILI with LPAM in two melanoma xenografts, DM443 and DM738, increasing quadrupling time 37% and 113%, respectively (P = 0.03). Immunohistochemical analyses of tumor specimens showed that pretreatment with systemic bevacizumab markedly increased LPAM-DNA adduct formation. Systemic treatment with bevacizumab before regional chemotherapy increases delivery of LPAM to tumor cells and represents a novel way to augment response to regional therapy for advanced extremity melanoma.

Neutrophil Gelatinase-Associated Lipocalin: A Superior Biomarker for Detection of Subclinical Acute Kidney Injury and Poor Prognosis

For 60 years, the current concept and diagnosis of acute kidney injury (AKI) have been based on increases in serum creatinine and decreases in urine output indicating loss of excretory renal function. At least, in part, this state is the result of the lack of real-time, easily clinically applicable, glomerular filtration measurement methods. Therefore, to date, AKI is classified using either the Risk, Injury, Failure, Loss of Function, Endstage Renal Disease (RIFLE) [1] or AKI network consensus criteria [2], both international consensus classifications. However, these classifications are as imperfect as their end points (serum creatinine and urine output). Thus, in a significant proportion of patients at renal risk, acute tubular damage might occur without loss of excretory function and remain undetected. Acute kidney injury is an epidemic and major clinical issue affecting up to 30% of hospitalized patients [3] with persistently high hospital re-admission and mortality rates of up to 60% [4]. There is an almost linear increase in mortality rates with an odds ratio of 10 for patients developing severe AKI [5]. Epidemiological studies suggest a strong relationship with ensuing chronic kidney disease and progression to end-stage renal disease, in at least 5–10% of patients necessitating lifelong dialysis or renal transplantation [6]. Expenses for treatment, care and possibly invalidity in patients with AKI account for a considerable proportion of costs in our healthcare system. It is increasingly acknowledged that AKI per se, may incite injury in distant organs, such as the lungs, with alterations in vascular permeability and pulmonary edema, and brain cell apoptosis [7,8]. The paucity of early structural injury biomarkers has hampered our ability to translate promising therapies from animal experiments to

A Potential Role for Angiopoietin 2 in the Regulation of the Blood–Retinal Barrier in Diabetic Retinopathy

Although VEGF has been identified as an important mediator of the blood-retinal barrier alteration in diabetic retinopathy, the hypothesis for this study was that that other molecules, including the angiopoietins (Ang-1 and -2), may play a role. The expression of angiopoietins was analyzed in an animal model of diabetic retinopathy, and the role of Ang-2 in the regulation of diabetes-induced alterations of vascular permeability was characterized. Diabetes was induced in rats, and human retinal endothelial cells (HRECs) were grown in media with 5.5 or 30.5 mM glucose. Levels of Ang-1 and -2 mRNA and protein were analyzed. Fluorescence-based assays were used to assess the effect of Ang-2 on vascular permeability in vivo and in vitro. The effect of Ang-2 on VE-cadherin function was assessed by measuring the extent of tyrosine phosphorylation. Ang-2 mRNA and protein increased in the retinal tissues after 8 weeks of diabetes and in high-glucose-treated cells. Intravitreal injection of Ang-2 in rats produced a significant increase in retinal vascular permeability. Ang-2 increased HREC monolayer permeability that was associated with a decrease in VE-cadherin and a change in monolayer morphology. High glucose and Ang-2 produced a significant increase in VE-cadherin phosphorylation. CONCLUSIONS; Ang-2 is upregulated in the retina in an animal model of diabetes, and hyperglycemia induces the expression of Ang-2 in isolated retinal endothelial cells. Increased Ang-2 alters VE-cadherin function, leading to increased vascular permeability. Thus, Ang-2 may play an important role in increased vasopermeability in diabetic retinopathy.

Mast Cells Increase Vascular Permeability by Heparin-Initiated Bradykinin Formation In Vivo

Activated mast cells trigger edema in allergic and inflammatory disease. We report a paracrine mechanism by which mast cell-released heparin increases vascular permeability invivo. Heparin activated the protease factor XII, which initiates bradykinin formation in plasma. Targeting factor XII or kinin B2 receptors abolished heparin-triggered leukocyte-endothelium adhesion and interfered with a mast cell-driven drop in blood pressure in rodents. Intravital laser scanning microscopy and tracer measurements showed heparin-driven fluid extravasation in mouse skin microvessels. Ablation of factor XII or kinin B2 receptors abolished heparin-induced skin edema and protected mice from allergen-activated mast cell-driven leakage. In contrast, heparin and activated mast cells induced excessive edema in mice deficient in the major inhibitor of factor XII, C1 esterase inhibitor. Allergen exposure triggered edema attacks in hereditary angioedema patients, lacking C1 esterase inhibitor. The data indicate that heparin-initiated bradykinin formation plays a fundamental role in mast cell-mediated diseases.