Hypersensitive blood vessels in Clarkson disease

Idiopathic systemic capillary leak syndrome (ISCLS) is a rare, recurrent condition with dramatically increased blood vessel permeability and, therefore, induction of systemic edema, which may lead to organ damage and death. In this issue of the JCI, Ablooglu et al. showed that ISCLS vessels were hypersensitive to agents known to increase vascular permeability, using human biopsies, cell culture, and mouse models. Several endothelium-specific proteins that regulate endothelial junctions were dysregulated and thereby compromised the vascular barrier. These findings suggest that endothelium-intrinsic dysregulation underlies hyperpermeability and implicate the cytoplasmic serine/threonine protein phosphatase 2A (PP2A) as a potential drug target for the treatment of ISCLS.

Intrinsic endothelial hyperresponsiveness to inflammatory mediators drives acute episodes in models of Clarkson disease

Clarkson disease, or monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS), is a rare, relapsing-remitting disorder featuring the abrupt extravasation of fluids and proteins into peripheral tissues, which in turn leads to hypotensive shock, severe hemoconcentration, and hypoalbuminemia. The specific leakage factor(s) and pathways in ISCLS are unknown, and there is no effective treatment for acute flares. Here, we characterize an autonomous vascular endothelial defect in ISCLS that was recapitulated in patient-derived endothelial cells (ECs) in culture and in a mouse model of disease. ISCLS-derived ECs were functionally hyperresponsive to permeability-inducing factors like VEGF and histamine, in part due to increased endothelial nitric oxide synthase (eNOS) activity. eNOS blockade by administration of N(γ)-nitro-l-arginine methyl ester (l-NAME) ameliorated vascular leakage in an SJL/J mouse model of ISCLS induced by histamine or VEGF challenge. eNOS mislocalization and decreased protein phosphatase 2A (PP2A) expression may contribute to eNOS hyperactivation in ISCLS-derived ECs. Our findings provide mechanistic insights into microvascular barrier dysfunction in ISCLS and highlight a potential therapeutic approach.

Capillary leak syndrome induced by the venoms of Russell's Vipers (Daboia russelii and Daboia siamensis) from eight locales and neutralization of the differential toxicity by three snake antivenoms

Snakebite envenomation caused by the Western and Eastern Russell's Vipers (Daboia russelii and Daboia siamensis) may potentially induce capillary leak syndrome (CLS), while the use of antivenom in treating this has not been well examined. This study investigated the CLS-inducing toxicity of Russell's Viper venoms from various sources and examined the neutralization activity of regionally available antivenoms, using a newly devised mouse model. D. russelii venoms demonstrated a more consistent vascular leakage activity (76,000-86,000 CLS unit of vascular leak index, a function of the diameter and intensity of Evans Blue dye extravasation into dermis) than D. siamensis venoms (33,000-88,000 CLS unit). Both species venoms increased hematocrits markedly (53-67%), indicating hemoconcentration. Regional antivenoms (DsMAV-Thailand, DsMAV-Taiwan, VPAV-India) preincubated with the venoms effectively neutralized the CLS effect to different extents. When the antivenoms were administered intravenously post-envenomation (challenge-rescue model), the neutralization was less effective, implying that CLS has a rapid onset that preceded the neutralizing activity of antivenom, and/or the antivenom has limited biodistribution to the venom's inoculation site. In conclusion, Russell's Viper venoms of both species from various locales induced CLS in mice. Antivenoms generally had limited efficacy in neutralizing the CLS effect. Innovative treatment for venom-induced CLS is needed.

Low hormone levels during an attack of systemic capillary leak syndrome normalizing after treatment

We report herein the case of a patient with low blood levels of different hormones during a systemic capillary leak syndrome (Clarkson's disease) attack.

3,39-Diindolylmethane Ameliorates Staphylococcal Enterotoxin B–Induced Acute Lung Injury through Alterations in the Expression of MicroRNA that Target Apoptosis and Cell-Cycle Arrest in Activated T Cells

3,39-Diindolylmethane (DIM), a natural indole found in cruciferous vegetables, has significant anti-cancer and anti-inflammatory properties. In this current study, we investigated the effects of DIM on acute lung injury (ALI) induced by exposure to staphylococcal enterotoxin B (SEB). We found that pretreatment of mice with DIM led to attenuation of SEB-induced inflammation in the lungs, vascular leak, and IFN-g secretion. Additionally, DIM could induce cell-cycle arrest and cell death in SEB-activated T cells in a concentration-dependent manner. Interestingly, microRNA (miRNA) microarray analysis uncovered an altered miRNA profile in lung-infiltrating mononuclear cells after DIM treatment of SEB-exposed mice. Moreover, computational analysis of miRNA gene targets and regulation networks indicated that DIM alters miRNA in the cell death and cell-cycle progression pathways. Specifically, DIM treatment significantly downregulated several miRNA and a correlative increase associated gene targets. Furthermore, overexpression and inhibition studies demonstrated that DIM-induced cell death, at least in part, used miR-222. Collectively, these studies demonstrate for the first time that DIM treatment attenuates SEB-induced ALI and may do so through the induction of microRNAs that promote apoptosis and cell-cycle arrest in SEB-activated T cells.

Increased myocardial extracellular volume in active idiopathic systemic capillary leak syndrome

BACKGROUND

The Systemic Capillary Leak Syndrome (SCLS) is a rare disorder of unknown etiology presenting as recurrent episodes of shock and peripheral edema due to leakage of fluid into soft tissues. Insights into SCLS pathogenesis are few due to the scarcity of cases, and the etiology of vascular barrier disruption in SCLS is unknown. Recent advances in cardiovascular magnetic resonance (CMR) allow for the quantitative assessment of the myocardial extracellular volume (ECV), which can be increased in conditions causing myocardial edema. We hypothesized that measurement of myocardial ECV may detect myocardial vascular leak in patients with SCLS.

METHODS

Fifty-six subjects underwent a standard CMR examination at the NIH Clinical Center from 2009 until 2014: 20 patients with acute intermittent SCLS, six subjects with chronic SCLS, and 30 unaffected controls. Standard volumetric measurements; late gadolinium enhancement imaging and pre- and post-contrast T1 mapping were performed. ECV was calculated by calibration of pre- and post-contrast T1 values with blood hematocrit.

RESULTS

Demographics and cardiac parameters were similar in both groups. There was no significant valvular disorder in either group. Subjects with chronic SCLS had higher pre-contrast myocardial T1 compared to healthy controls (T1: 1027 ± 44 v. 971 ± 41, respectively; p = 0.03) and higher myocardial ECV than patients with acute intermittent SCLS or controls: 33.8 ± 4.6, 26.9 ± 2.6, 26 ± 2.4, respectively; p = 0.007 v. acute intermittent; P = 0.0005 v. controls). When patients with chronic disease were analyzed together with five patients with acute intermittent disease who had just experienced an acute SCLS flare, ECV values were significantly higher than in subjects with acute intermittent SCLS in remission or age-matched controls and (31.2 ± 4.6 %, 26.5 ± 2.7 %, 26 ± 2.4 %, respectively; p = 0.01 v. remission, p = 0.001 v. controls). By contrast, T1 values did not distinguish these three subgroups (1008 ± 40, 978 ± 40, 971 ± 41, respectively, p = 0.2, active v. remission; p = 0.06 active v. controls). Abundant myocardial edema without evidence of acute inflammation was detected in cardiac tissue postmortem in one patient.

CONCLUSIONS

Patients with active SCLS have significantly higher myocardial ECV than age-matched controls or SCLS patients in remission, which correlated with histopathological findings in one patient.

Endothelial Expression of Endothelin Receptor A in the Systemic Capillary Leak Syndrome

Idiopathic systemic capillary leak syndrome (SCLS) is a rare and potentially fatal vascular disorder characterized by reversible bouts of hypotension and edema resulting from fluid and solute escape into soft tissues. Although spikes in permeability-inducing factors have been linked to acute SCLS flares, whether or not they act on an inherently dysfunctional endothelium is unknown. To assess the contribution of endothelial-intrinsic mechanisms in SCLS, we derived blood-outgrowth endothelial cells (BOEC) from patients and healthy controls and examined gene expression patterns. Ednra, encoding Endothelin receptor A (ETA)-the target of Endothelin 1 (ET-1)-was significantly increased in SCLS BOEC compared to healthy controls. Although vasoconstriction mediated by ET-1 through ETA activation on vascular smooth muscle cells has been well characterized, the expression and function of ETA receptors in endothelial cells (ECs) has not been described. To determine the role of ETA and its ligand ET-1 in SCLS, if any, we examined ET-1 levels in SCLS sera and functional effects of endothelial ETA expression. ETA overexpression in EAhy926 endothelioma cells led to ET-1-induced hyper-permeability through canonical mechanisms. Serum ET-1 levels were elevated in acute SCLS sera compared to remission and healthy control sera, suggesting a possible role for ET-1 and ETA in SCLS pathogenesis. However, although ET-1 alone did not induce hyper-permeability of patient-derived BOEC, an SCLS-related mediator (CXCL10) increased Edrna quantities in BOEC, suggesting a link between SCLS and endothelial ETA expression. These results demonstrate that ET-1 triggers classical mechanisms of vascular barrier dysfunction in ECs through ETA. Further studies of the ET-1-ETA axis in SCLS and in more common plasma leakage syndromes including sepsis and filovirus infection would advance our understanding of vascular integrity mechanisms and potentially uncover new treatment strategies.

Clarkson disease - systemic capillary leak syndrome in a 6-year-old girl: case report

Idiopathic systemic capillary leak syndrome is a rare and life-threatening disorder of unknown pathology. It results from leakage of plasma from the intravascular into the interstitial space and is characterised by recurrent episodes of shock, weight gain and generalised oedema. Recurrent episodes of this syndrome are reported in a 6-year-old girl who presented with the characteristic symptoms of shock, oedema and hypoalbuminaemia. She was treated effectively with fluid resuscitation, ionotropes and intravenous immunoglobin. Since systemic capillary leak syndrome is rare and the diagnosis is often missed, further research regarding its pathogenesis and treatment in children is warranted.

Histone deacetylase inhibitors trichostatin A and suberoylanilide hydroxamic acid attenuate ventilator-induced lung injury

The pathophysiology of ventilator-induced lung injury (VILI) involves multiple mechanisms including inflammation. Histone deacetylase inhibitors have been shown to exert anti-inflammation activity. The purpose of this study was to examine the protecting roles and mechanisms of the histone deacetylase inhibitors trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA) in ventilator-induced lung injury in normal rat lung. Male Sprague-Dawley rats were divided into four groups: lung-protective ventilation (LV), injurious ventilation (HV), HV+TSA and HV+ SAHA groups. Mechanical ventilation (MV) settings were 7 ml/kg VT and 3cm H2O positive end-expiratorypressure [PEEP], 40 breaths/min for LV group and 42 ml/kg VT, zero end-expiratoryvolume [ZEEP], 40 breaths/min for the HV, HV+TSA and HV+ SAHA groups. After 2 h of MV, acute lung injury (ALI) score, wet-to-dry (W/D) weight ratio and the activity of myeloperoxidase (MPO) were determined. The concentration of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-10 (IL-6) in the homogenized lung were measured by ELISA. The expression ICAM-1 was measured by both realtime PCR and Western blot assays. In addition, survival of each group was also assessed. Our results indicated that administration of TSA or SAHA alleviated ventilator-induced lung injury. This was accompanied by reduced neutrophil infiltration, reduced MPO activity, decreased intercellular adhesion molecule-1 (ICAM-1) expression in lung tissue, and lower TNF-alpha, IL-1beta and IL-6 levels. In addition, treatment with HDAC inhibitors significantly prolonged the survival time of ventilator-induced lung injury rats. Our data suggested that TSA and SAHA could significantly alleviate ventilator-induced rat lung injury and prolong the survival time of those rats by attenuate intrapulmonary inflammatory response.

Comparison of vascular leak syndrome in mice treated with IL21 or IL2

Interleukin 21 (IL21) is a T-cell-derived 4-helix-bundle cytokine that has sequence homology to the IL2 family. Recombinant human interleukin 2 (rIL2) is approved for the treatment of metastatic melanoma and renal cell carcinoma. However, toxicity of rIL2, including induction of vascular leak syndrome (VLS), has limited use of this cytokine to a small proportion of eligible patients. Both rIL2 and murine IL21 (mIL21) have potent antitumor efficacy in murine models. The purpose of the current study was to compare the ability of mIL21 and rIL2 to induce vascular leakage in a mouse model. Pulmonary and hepatic uptake of Evans blue dye, serum cytokine levels, spleen cell immunophenotype, and histologic changes in lung and liver were evaluated to detect VLS. High-dose (200 μg) rIL2 treatment induced vascular leakage in mice, evidenced by inflammatory cell infiltration and fluid extravasation into the lung and liver and increased levels of TNFα, IFNγ, IL5, MCP1, and IL6 in serum. In contrast, an equivalent dose of mIL21 resulted in minimal vascular leakage with no evidence of cytopenia or cytokine production. These results support the use of IL21 as a cancer immunotherapeutic agent, potentially providing an antitumor response without induction of VLS.

Blockade of hyaluronan inhibits IL-2-induced vascular leak syndrome and maintains effectiveness of IL-2 treatment for metastatic melanoma

Vascular leak syndrome (VLS) is a life-threatening toxicity induced during IL-2 treatment of cancer patients. The mechanism of IL-2-induced VLS is still poorly understood. At present, there is no specific therapy for VLS. Previous studies from our laboratory demonstrated that hyaluronan (HA), a large glycosaminoglycan, abundant in the extracellular matrix and on the cell surface, caused a marked increase of IL-2-induced VLS in the lungs and liver of C57BL/6 mice. Conversely, blockade or knockout of its major receptor, CD44, resulted in a marked decrease of VLS, thereby suggesting a role for HA in VLS. In this study, we report a novel means to prevent IL-2-induced VLS by blocking endogenous HA with HA-specific binding peptide, Pep-1, a newly isolated peptide which specifically binds to soluble, cell-associated, and immobilized forms of HA. Our results demonstrated that blocking HA with Pep-1 dramatically inhibited IL-2-induced VLS in both normal mice as well as in mice bearing melanoma. Moreover, Pep-1 treatment maintained the effectiveness of IL-2 and prevented the metastasis of melanoma. IL-2-induced emigration of lymphocytes across the endothelium and cytotoxicity against tumor by lymphokine-activated killer cells were not affected by Pep-1. Instead, use of Pep-1 maintained endothelial integrity and reduced their apoptosis during IL-2-induced VLS. These data suggested that HA plays a critical role in regulating endothelial cell damage and induction of IL-2-mediated VLS. Also, blockade of HA using Pep-1 could constitute a novel therapeutic modality to prevent IL-2-mediated toxicity, thereby facilitating the effectiveness of high-dose IL-2 in the treatment of metastatic melanomas.

Suppression of endotoxin-induced inflammation by taxol

The pathogenesis of acute lung injury includes transendothelial diapedesis of leukocytes into lung tissues and disruption of endothelial/epithelial barriers leading to protein-rich oedema. In vitro studies show that the microtubule network plays a role in the regulation of endothelial permeability as well as in neutrophil locomotion. It was hypothesised that the microtubule-stabilising agent, taxol, might attenuate inflammation and vascular leak associated with acute lung injury in vivo. The effect of intravenously delivered taxol was assessed using a model of murine lung injury induced by intratracheal lipopolysaccharide (LPS) administration. Parameters of lung injury and inflammation were assessed 18 h after treatment. Intravenously delivered taxol significantly reduced inflammatory histological changes in lung parenchyma and parameters of LPS-induced inflammation: infiltration of proteins and inflammatory cells into bronchoalveolar lavage fluid, lung myeloperoxidase activity, and extravasation of Evans blue-labelled albumin into lung tissue. Taxol alone (in the absence of LPS) had no appreciable effect on these parameters. In addition to lung proteins, intravenous taxol reduced accumulation of leukocytes in ascitic fluid in a model of LPS-induced peritonitis. Taken together, the present data demonstrate that microtubule stabilisation with taxol systemically attenuates lipopolysaccharide-induced inflammation and vascular leak.

Constitutive expression of IL-2Rbeta chain and its effects on IL-2-induced vascular leak syndrome

IL-2-induced vascular leak syndrome (VLS) is an important mechanism explaining the toxic effects of this cytokine and limiting its therapeutic use. We previously characterized a mouse model of IL-2-induced pulmonary VLS used to demonstrate that NK lymphocytes are involved in early/acute phase VLS (after one IL-2 injection). We also showed that NK cells and polymorphonuclear neutrophils (PMN) are involved in the late/chronic phase of the syndrome (after four daily IL-2 injections). In this study we use our mouse model to evaluate the role played by the IL-2 receptor (IL-2R) in VLS induction. Mouse and human IL-2R are different since the mouse IL-2Rbeta chain does not recognize IL-2. Here, we compare the acute and late VLS responses in human IL-2Rbeta transgenic and C57BL/6 wild type mice. Parameters linked to early phase VLS (bronchoconstriction and PMN mobilization) are enhanced in human IL-2Rbeta transgenic mice. By contrast, parameters used to measure late events (protein leakage and edema) are similar in human IL-2Rbeta transgenic mice and C57BL/6 wild type animals. However, after four IL-2 injections, the cellular content of the bronchoalveolar lavage fluids was different between the two types of animals. This study also characterizes a humanized animal model that could be further used to study human IL-2 activity and side effects in vivo.

Plasma vascular endothelial growth factor in severe sepsis

Vascular endothelial growth factor (VEGF) is a potent vascular permeability factor. The development of capillary leak is common in septic patients, and several sepsis-associated mediators may induce VEGF production. The potential role of VEGF during sepsis has not been studied to date. The aim of the study was first to assess whether circulating VEGF levels increase during sepsis, and second, to examine whether plasma VEGF levels are associated with disease severity. VEGF levels were measured in serial plasma samples of 18 patients with severe sepsis and in 40 healthy controls. VEGF levels were correlated to clinical signs and symptoms. VEGF levels were significantly elevated in sepsis patients compared with healthy controls (134 vs. 55 pg/mL; P <0.001). Serum albumin levels used as an indirect measure of vascular leak were decreased in septic patients. Increased plasma VEGF levels at study entry were correlated to severity of multiple organ dysfunction during the course of disease (Pearson correlation coefficient r=0.75; P=0.001). Moreover, maximum VEGF levels in nonsurvivors were significantly higher than those in survivors (P=0.018). These data show that plasma VEGF levels are elevated during severe sepsis. Furthermore, our data indicate that plasma VEGF levels are associated with disease severity and mortality. Further study of the potential role of VEGF in the development of sepsis-associated capillary leak is indicated.

Idiopathic systemic capillary leak syndrome: cutaneous involvement can be misleading

BACKGROUND

Systemic capillary leak syndrome (SCLS) is a severe disorder characterized by unexplained rapid transfer of considerable volumes of plasma from the intravascular to the extravascular compartment. For some cases of SCLS, no aetiology is evident and these cases are reported as idiopathic (ISCLS).

OBJECTIVES

To describe the cutaneous findings in 3 patients with ISCLS.

RESULTS

Cutaneous involvement consisted in sclerosis, livedo, purpura and photodistributed maculopapular erythematous rash. Dermal mucinosis was proven by biopsy in 1 patient. No underlying disease was diagnosed during follow-up.

CONCLUSION

The above-mentioned cutaneous findings can be present during acute attacks of ISCLS. They seem specifically related to the ISCLS and not indicative of an underlying disease.

Capillary leak syndrome induced by acitretin

The mucocutaneous side-effects of systemic retinoids are well known. We report a patient with diffuse oedema, which is a very rare side-effect of retinoids. The pathophysiology of this condition is poorly known because of the rarity of relevant observations, but apparently corresponds to capillary leak syndrome. The outcome is invariably favourable following withdrawal of the drug, which should be definitively contraindicated in the patient.

Proinflammatory cytokines and their role in the development of major transplant-related complications in the early phase after allogeneic bone marrow transplantation

Serum levels of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor (TNF)-alpha were frequently measured during the first 30 days after allogeneic bone marrow transplantation (BMT) in 84 consecutive adult patients. Major transplant-related complications (MTCs) occurred in 33% of cases and included veno-occlusive liver disease, idiopathic pneumonia syndrome, severe endothelial leakage syndrome and >grade II acute graft-versus-host disease. Compared with patients having minor complications, those with MTCs developed higher levels at times of maximal clinical signs (all cytokines, P<0.001), between days 0-5 post-BMT (IL-6 and IL-8, P<0.05) and days 6-10 (L-6, P<0.001; IL-8 and TNF, P<0.01) post-BMT. We could not discriminate patterns of cytokine release that were specific for any subtype of MTC. Higher levels of IL-8 during days 0-5 were associated (P=0.044) with early (<40 days) death. Multivariate analysis including patient and transplant characteristics as well as post-BMT levels of C-reactive protein showed that high average levels of one or more of the cytokines within the first 10 days post-BMT were independently associated with MTC (Odd's ratio: 2.3 [1.2-4.5], P=0.011). This study shows that systemic release of proinflammatory cytokines contributes to the development of MTC and provides a rationale for pre-emptive anti-inflammatory treatment in selected patients.

Vascular leak syndrome of Sprague-Dawley rats in a mandibular distraction osteogenesis study

Vascular leak syndrome (VLS) is a common and often fatal sequela of multiple bone traumas, and of infectious, toxic, and allergic insults in human patients. Although an animal model for VLS has not been fully established, rats have shown sensitivity to the syndrome that approximates that of the human population. We describe cases of VLS in three-month-old adult and one-month-old Sprague-Dawley rats in an osteogenesis study aimed at optimizing correction of bone hypoplasias and other craniofacial deformities in children, using a mandibular distraction device. In the study reported here, VLS was diagnosed in 40% of the rats that were necropsied after dying or being euthanized early, subsequent to mandibular osteotomy, a procedure that involves minimal bone trauma. The gross and histologic findings, as well as the clinical course of VLS in the rats of the osteogenesis study, were similar to those of documented human cases. Hence, the rat may be a useful animal model to h elp characterize the physiologic and molecular events that accompany this syndrome.

ZO-1 redistribution and F-actin stress fiber formation in pulmonary endothelial cells after thermal injury

BACKGROUND

In response to isolated inflammatory stimuli, changes in endothelial cell morphology that enhance paracellular flow of solutes result from F-actin stress fiber formation, myosin phosphorylation, and actin anchoring protein (ZO-1) modifications. We hypothesized that myosin light chain kinase inhibition would diminish burn-enhanced endothelial monolayer permeability by secondarily preventing F-actin and actin anchoring protein rearrangements.

METHODS

Human pulmonary microvascular endothelial cells were treated for 4 hours with 20% human burn serum (isolated from patients with > 45% total body surface area thermal injury or healthy volunteers). Select cultures were pretreated with myosin light chain kinase inhibitors (ML-9). Permeability was assessed by migration of bovine serum albumin across cell monolayers. Cells were stained with rhodamine-phalloidin and anti-ZO-1 antisera and examined by means of confocal microscopy.

RESULTS

Burn serum significantly enhanced monolayer permeability to albumin, whereas pretreatment with ML-9 limited this effect. Control cells maintained cortical F-actin and peripheral ZO-1 distributions (1a, b), whereas burn serum induced transcellular F-actin stress fiber formation and a diffuse ZO-1 staining (2a, b). ML-9 prevented burn-induced actin rearrangements, but not the diffuse redistribution of ZO-1.

CONCLUSION

These data demonstrate that endothelial F-actin stress fiber formation and ZO-1 redistribution contribute to postburn loss of pulmonary endothelial monolayer integrity. Although myosin phosphorylation appears to be required for endothelial F-actin stress fiber formation, redistribution of actin-membrane anchoring proteins appears to be regulated independently after thermal injury.

Toxigenic Helicobacter pylori induces changes in the gastric mucosal microcirculation in rats

BACKGROUND AND AIMS

One of the key components of inflammation is changes in vascular structure and function. This suggests that the microcirculation may be a key target of Helicobacter pylori released factors. It has previously been shown in vivo that pooled H pylori extracts from duodenal ulcer/gastritis patients induce platelet aggregation but no leucocyte activation within rat gastric mucosal microcirculation (GMMC). However, infection with strains associated with ulcer disease as compared with gastritis may exert greater effects on the microcirculation. This study used fluorescent in vivo microscopy to determine the acute effects of extracts of genotypically different H pylori strains on the GMMC.

METHODS

Three H pylori extracts, with different cagA and VacA toxigenic status, were individually administered to the gastric mucosa of anaesthetised Wistar rats. The mucosal surface was visualised via an incision made in the exteriorised stomach. Fluoroscein isothiocyanate conjugated to bovine serum albumin (FITC-BSA) or acridine orange was used to quantify macromolecular leak (MML) and leucocyte/platelet activity respectively for 120 minutes. Changes in capillary and post-capillary venule (PCV) diameters were also monitored.

RESULTS

The cagA(+) VacA toxigenic strain 60190 induced significant and sustained MML by five minutes (p<0.01). Transient and less leakage was observed with its isogenic VacA(-) mutant and other non-toxigenic strains regardless of cagA status. Significant increases in leucocyte adhesion (p<0.05), platelet aggregation (p<0.05), and PCV vasoconstriction (p<0.05) were only observed with the cag A(+) and toxigenic strain.

CONCLUSION

Extracts of H pylori are capable of inducing marked disturbances within the rat GMMC. These disturbances seem to be dependent on the production of an active vacuolating cytotoxin. Varying effects on the GMMC may explain the clinically diverse outcomes associated with genotypically different strains.

[Follow-up of proliferation of juxtapapillary retinal pigment epithelium]

PURPOSE

Bengin proliferation of the juxtapapillary retinal pigment epithelium is a rare but important tumor because it may be mistaken for a malignant lesion such as choroidal melanoma.

CASE REPORT

A 9-year-old male patient consulted our clinic first in 1991 because of a reduction in visual acuity due to a tumor of the optic nerve head in the left eye. Visual acuity was 1.0 in the right eye and 0.2 in the left eye. Slit lamp examination and intraocular pressure were regular in both eyes. Kinetic perimetry showed a enlarged blind spot besides regular isopters. Funduscopy revealed a pigmented, ill-defined prominence of the optic nerve head with a mossy surface. In annual examinations were found a slowly progredient reduction in visual acuity up to 0.04 durning the last visit in January 2000 as well as a enlargement of the blind spot due to an increasing prominence and pigmentation of the optic nerve head. Because of the clincal aspect, the slowly progressive course, the enlargement of the blind spot with deterioration of vision and especially the florescein angiography, which revealed peripapillary capillary alterations with leakage, we diagnosed a proliferation of the juxtapapillary retinal pigment epithelium.

CONCLUSION

The proliferation of the juxtapapillary retinal pigment epithelium can be differentiated from other pigmented tumors of the optic nerve head by its typical clinical aspect and course and especially by using flourescein angiography.

Initial evidence of endothelial cell apoptosis as a mechanism of systemic capillary leak syndrome

BACKGROUND

Systemic capillary leak syndrome (SCLS) is a rare disorder of unknown etiology that is characterized by acute recurrent attacks of hypovolemic shock commonly following an inflammatory stimulus such as a viral illness. Prophylactic therapy is generally ineffective, and the outcome is frequently fatal.

METHODS

In order to investigate the cellular mechanisms leading to SCLS, we examined the effects of sera from two patients with active SCLS on microvascular endothelial cell apoptosis in vitro. Apoptosis was determined by morphologic criteria, DNA fragmentation, annexin V stain, and by a quantitative photometric assay. The apoptotic pathway was investigated by Western blot of endothelial cells lysate after exposure to SCLS sera.

RESULTS

The sera from patients with active SCLS mediated profound apoptosis of microvascular endothelial cells shortly after exposure. The exposed microvascular endothelial cells underwent immediate apoptosis as evidenced by morphologic changes, plasma membrane phosphatidylserine exposure, and by DNA fragmentation. Increased Bax/Bcl-2 ratio in endothelial cells exposed to SCLS sera was observed and suggested an oxidation injury as the possible mechanism for endothelial apoptosis. This potential mechanism was further explored by measuring intracellular reactive oxygen species (ROS) following SCLS serum exposure. Sera from both patients caused marked increases in ROS, initially detectable at 1 h and persisted for at least 12 h, with control serum from healthy subjects showing no effect on basal endothelial cell ROS concentrations.

CONCLUSION

Components from the sera of patients with active systemic capillary leak syndrome in contrast to healthy subject sera mediate early and extensive endothelial apoptosis in vitro that is associated with oxidation injury. These data represent compelling initial evidence for oxidation-induced apoptosis as a likely mechanism for endothelial injury leading to SCLS.

C1 inhibitor prevents capillary leakage after thermal trauma

OBJECTIVE

In burned patients, activation of the complement and clotting systems is suggested to play an important role in the development of the capillary leak syndrome and inflammatory tissue destruction. In an animal model of thermal trauma, the possible protective effect of C1 inhibitor (C1Inh), a major control protein of both the complement and clotting systems, was investigated.

DESIGN

Prospective, controlled study.

SETTING

Animal model.

SUBJECTS

Healthy pigs weighing 30 kg.

INTERVENTIONS

Pigs were scalded for 25 secs with 75 degrees C hot water to achieve a 30% total body surface deep partial-thickness burn. The treatment group (n = 8) received C1Inh concentrate at an initial dose of 100 units/kg body weight immediately after thermal trauma, followed by three further applications every 12 hrs. Two control groups included animals that were either scalded (n = 8) or not scalded (n = 7) and treated with lactated Ringer's solution.

MEASUREMENTS

Before and at various time points after trauma blood samples were analyzed for complement activation (APH50, CH50, SC5b-9, C3). Continuous monitoring of hemodynamic variables was performed and postmortem histologic examination of specimens from lung, heart, liver, kidney, stomach, duodenum, jejunum, ileum, and colon was carried out. Aseptically collected mesenteric lymph nodes were pooled and screened for bacterial translocation. For evaluation of the burn wound, biopsies from defined scalded and not scalded areas were taken daily. As a measure for edema formation, the weight of the animals was recorded every 2 hrs.

RESULTS

After C1Inh treatment, which led to a significantly reduced complement activation, the clinical outcome was clearly improved, as indicated by vital signs and as demonstrated by reduced edema formation. Treated animals presented a diminished bacterial translocation. Pathologic alterations were clearly diminished in the burned skin, in shock-related organs, and in the intestines.

CONCLUSION

Application of C1Inh appears to be an effective means to prevent capillary leakage and inflammatory tissue destruction after thermal trauma.

Evidence for the involvement of CD44 in endothelial cell injury and induction of vascular leak syndrome by IL-2

At sites of chronic inflammation seen during infections, autoimmunity, graft-vs-host response, and cytokine therapy, endothelial cell injury is known to occur, the exact mechanism of which is unknown. In the current study we used IL-2-induced vascular leak syndrome (VLS) as a model to investigate whether cytotoxic lymphocytes use CD44 in mediating endothelial cell injury. Administration of IL-2 to wild-type mice triggered significant VLS in the lungs and liver. In contrast, in CD44 knockout (KO) mice, IL-2-induced VLS was markedly reduced in the lungs and liver. IL-2-treated wild-type and CD44 KO mice had similar levels of perivascular infiltration with lymphocytes in the lungs and liver. This suggested that the decrease in VLS seen in CD44 KO mice was not due to the inability of lymphocytes to migrate to these organs. Ultrastructural studies demonstrated extensive endothelial cell damage in the lungs and liver of IL-2-treated wild-type, but not CD44 KO, mice. Moreover, CD44-KO mice exhibited a marked decrease in IL-2-induced lymphokine-activated killer cell activity. The induction of VLS was dependent on the expression of CD44 on immune cells rather than endothelial cells because adoptive transfer of CD44+, but not CD44- spleen cells along with IL-2 into CD44 KO mice triggered VLS. The IL-2-induced VLS was blocked by administration of F(ab')2 of Abs against CD44. The current study demonstrates that CD44 plays a key role in endothelial cell injury. Blocking CD44 in vivo may offer a novel therapeutic approach to prevent endothelial cell injury by cytotoxic lymphocytes in a variety of clinical disease models.

Lethal capillary leak syndrome after a single administration of interferon beta-1b

Interferon beta-1b (IFNbeta-1b) is a potent immunomodulatory drug in the treatment of MS. We report a lethal capillary leak syndrome after the administration of IFNbeta-1b in a patient with disseminated white matter disease, monoclonal gammopathy, and acquired C1 inhibitor (C1-INH) deficiency. IFNbeta-1b may cause a transient release of proinflammatory cytokines finally resulting in an uninhibited activation of the complement cascade in patients with C1-INH deficiency.

Evidence for a structural motif in toxins and interleukin-2 that may be responsible for binding to endothelial cells and initiating vascular leak syndrome

The dose-limiting toxicity of interleukin-2 (IL-2) and immunotoxin (IT) therapy in humans is vascular leak syndrome (VLS). VLS has a complex etiology involving damage to vascular endothelial cells (ECs), extravasation of fluids and proteins, interstitial edema, and organ failure. IL-2 and ITs prepared with the catalytic A chain of the plant toxin, ricin (RTA), and other toxins, damage human ECs in vitro and in vivo. Damage to ECs may initiate VLS; if this damage could be avoided without losing the efficacy of ITs or IL-2, larger doses could be administered. In this paper, we provide evidence that a three amino acid sequence motif, (x)D(y), in toxins and IL-2 damages ECs. Thus, when peptides from RTA or IL-2 containing this sequence motif are coupled to mouse IgG, they bind to and damage ECs both in vitro and, in the case of RTA, in vivo. In contrast, the same peptides with a deleted or mutated sequence do not. Furthermore, the peptide from RTA attached to mouse IgG can block the binding of intact RTA to ECs in vitro and vice versa. In addition, RTA, a fragment of Pseudomonas exotoxin A (PE38-lys), and fibronectin also block the binding of the mouse IgG-RTA peptide to ECs, suggesting that an (x)D(y) motif is exposed on all three molecules. Our results suggest that deletions or mutations in this sequence or the use of nondamaging blocking peptides may increase the therapeutic index of both IL-2, as well as ITs prepared with a variety of plant or bacterial toxins.

Complement activation in relation to capillary leakage in children with septic shock and purpura

To assess the relationship between capillary leakage and inflammatory mediators during sepsis, blood samples were taken on hospital admission, as well as 24 and 72 h later, from 52 children (median age, 3.3 years) with severe meningococcal sepsis, of whom 38 survived and 14 died. Parameters related to cytokines (interleukin 6 [IL-6] IL-8, plasma phospholipase A2, and C-reactive protein [CRP]), to neutrophil degranulation (elastase and lactoferrin), to complement activation (C3a, C3b/c, C4b/c, and C3- and C4-CRP complexes), and to complement regulation (functional and inactivated C1 inhibitor and C4BP) were determined. The degree of capillary leakage was derived from the amount of plasma infused and the severity of disease by assessing the pediatric risk of mortality (PRISM) score. Levels of IL-6, IL-8, C3b/c, C3-CRP complexes, and C4BP on admission, adjusted for the duration of skin lesions, were significantly different in survivors and nonsurvivors (C3b/c levels were on average 2.2 times higher in nonsurvivors, and C3-CRP levels were 1.9 times higher in survivors). Mortality was independently related to the levels of C3b/c and C3-CRP complexes. In agreement with this, levels of complement activation products correlated well with the PRISM score or capillary leakage. Thus, these data show that complement activation in patients with severe meningococcal sepsis is associated with a poor outcome and a more severe disease course. Further studies should reveal whether complement activation may be a target for therapeutical intervention in this disease.

Induction of nitric oxide synthase by lipopolysaccharide inhalation enhances substance P-induced microvascular leakage in guinea-pigs

Inducible nitric oxide (NO) synthase (iNOS)-mediated hyperproduction of NO in airways has been reported in asthmatic patients. However, the role of NO in the pathogenesis of asthma has not yet been fully elucidated. The aim of this study was to examine whether the iNOS-derived NO affects airway microvascular leakage, one of the characteristic features of asthmatic airway inflammation. Guinea-pigs were exposed to lipopolysaccharide (LPS) (1 mg x mL(-1)) by inhalation in order to induce iNOS in the airways, and the histochemical staining of reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase activity was determined 5 h after the inhalation to confirm the iNOS induction. Airway microvascular leakage to subthreshold doses of substance P (0.3 microg x kg(-1), i.v.) was also examined in the absence and presence of an iNOS inhibitor (aminoguanidine) in LPS- or saline-exposed (control) animals using Evans blue dye and Monastral blue dye. In the LPS-exposed animals, increased NADPH-diaphorase activity was observed in the airway microvasculature compared with the control animals. Substance P caused significant airway microvascular leakage assessed by Evans blue dye in all airway levels in the LPS-exposed animals but not in the control group. This was also confirmed by Monastral blue dye extravasation. Aminoguanidine abolished this LPS-induced enhancement of plasma leakage to substance P without changing the systemic blood pressure. These results may suggest that inducible nitric oxide synthase-derived nitric oxide is capable of potentiating neurogenic plasma leakage in airways.

Evidence for the involvement of Fas ligand and perforin in the induction of vascular leak syndrome

Endothelial cell injury resulting in vascular leak syndrome (VLS) is one of the most widely noted phenomenons in a variety of clinical diseases. In the current study we used IL-2-induced VLS as a model to investigate the role of cytolytic lymphocytes in the cytotoxicity of endothelial cells. Administration of IL-2 (75,000 U/mouse, three times a day for 3 days) into BL/6 wild-type mice triggered significant VLS in the lungs, liver, and spleen. Interestingly, perforin-knockout (KO) mice exhibited a marked decrease in IL-2-induced VLS in all three organs tested. Also, Fas ligand-defective (gld) mice and Fas-deficient (lpr) mice exhibited decreased VLS in the liver and spleen, but not in the lungs. The decreased VLS seen in perforin-KO, gld, and lpr mice was not due to any defect in lymphocyte migration or homing to various organs because histopathologic studies in these mice demonstrated significant and often greater perivascular infiltration of lymphocytes compared with the IL-2-treated wild-type mice. Ultrastructural studies of the lungs demonstrated significant damage to the endothelial cells in IL-2-treated wild-type mice and decreased damage in perforin-KO mice. IL-2 administration caused up-regulation of CD44 in all strains of mice tested and triggered increased LAK activity against an endothelial cell line in wild-type and gld mice, but not in perforin-KO mice. The current study demonstrates for the first time that perforin and Fas ligand may actively participate in endothelial cell injury and induction of VLS in a variety of organs.

Systemic capillary leak syndrome: where does the fluid go?

Images

Comparison of diltiazem and verapamil on rat microvascular permeability

Calcium channel antagonists are among the most widely prescribed cardiovascular drugs. Their benefit is limited by the side effect of edema, the microvascular mechanism of which is not known. We compared the local effect on edema formation in rat skin and skeletal muscle of two calcium channel antagonists, diltiazem and verapamil, and determined if the edema effect correlated with changes in microvascular flow. An increase in microvascular flow can potentiate edema formation by increasing microvascular hydrostatic pressure and the proportion of the bed that is perfused. Diltiazem, but not verapamil or control, injected s.c. in scrotal skin caused plasma albumin leakage visualized as local bluing of tissue in rats that had been pretreated with Evans blue dye systemically. Topographic studies using Monastral blue dye showed that in the underlying cremaster muscle, diltiazem increased leakage of dye particles not from capillaries but from postcapillary venules. The postcapillary venule is associated with inflammatory edema, suggesting a direct effect of diltiazem on endothelial permeability. The local injection of diltiazem also increased significantly (P < 0.05) plasma leakage quantified as the local accumulation of systemically injected 125I-radiolabeled albumin, from 14.5 +/- 2.0 and 6.9 +/- 1.0 microliters in control sites to 30.0 +/- 7.3 and 18.0 +/- 2.5 microliters in dorsal skin and abdominal rat skin, respectively. In contrast, verapamil at similar doses did not increase plasma albumin leakage significantly. At the doses that caused local skin edema, diltiazem had less effect on microvascular skin blood flow, measured by a laser Doppler flow probe, (12.6 +/- 5.3% at 15 min and 2.8 +/- 8.4% change at 30 min) than verapamil (39.0 +/- 7.3% at 15 min 30.0 +/- 6.7% change at 30 min, P < 0.01). The microvascular effects of these two calcium channel antagonists differ in that diltiazem had a significant effect on microvascular permeability whereas verapamil had a significant effect on microvascular blood flow.

The role of active inducible nitric oxide synthase expression in the pathogenesis of capillary leak syndrome resulting from interleukin-2 therapy in mice

Previously, we showed that nitric oxide (NO) plays a major role in the pathogenesis of IL-2-induced capillary leak syndrome in healthy or mammary adenocarcinoma-bearing C3H/HeJ mice. NO synthase (NOS) inhibitors, such as NG-nitro-L-arginine methyl ester (L-NAME) reduced all the manifestations of IL-2-induced capillary leakage, without compromising the antitumor effects of IL-2. The present study was carried out on healthy C3H/HeJ mice subjected to one or two 4-day rounds of systemic IL-2 therapy with or without oral L-NAME therapy to: (a) identify the tissue source of NOS activity and NOS protein induced by IL-2 therapy; (b) identify histologically the nature of the structural damage to the lungs associated with IL-2 therapy-induced pulmonary edema; and (c) evaluate the effects of additional L-NAME therapy on the above-mentioned parameters. Results revealed that IL-2 therapy in healthy mice resulted in the expression of inducible NOS in numerous tissues including the endothelium and muscles of the anterior thoracic wall as well as splenic macrophages. One round of IL-2 therapy resulted in high levels of inducible NOS (iNOS) activity in the anterior thoracic wall accompanied by pleural effusion. After two rounds of IL-2 therapy, there was neither pleural effusion nor high iNOS activity in the thoracic wall. IL-2-induced pulmonary edema after one round of therapy correlated to both a significant rise in NO production measured in the serum and structural damage to the lungs and its capillaries. Addition of the NOS inhibitor L-NAME totally eradicated NOS activity but not necessarily iNOS expression. It also reduced IL-2-induced pulmonary edema and pleural effusion, restrained the rise in the levels of NO metabolites (nitrites and nitrates) in the serum and pleural effusion, and significantly restored the structural integrity of the lungs after one round of therapy. Thus, NOS inhibitors may be beneficial adjuncts to IL-2 therapy for cancer and infectious diseases.