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.

Unlocking endothelial barrier restoration: FX06 in systemic capillary leak syndrome and beyond.

Increased vascular permeability is a prevalent feature in a wide spectrum of clinical conditions, but no effective treatments to restore the endothelial barrier are available. Idiopathic systemic capillary leak syndrome (ISCLS) is a life-threatening Paroxysmal Permeability Disorder characterized by abrupt, massive plasma extravasation. This condition serves as a robust model for investigating therapeutic approaches targeting interendothelial junctions. We conducted a single-center, interventional in vitro study at the Referral Center for ISCLS in Italy, involving four diagnosed ISCLS patients, aiming at investigating the effects of FX06, a Bß15-42 fibrin-derived peptide binding to VE-Cadherin, on endothelial barrier exposed to intercritical and acute ISCLS sera. The Transwell Permeability Assay was used to assess the permeability of human umbilical vein endothelial cells (HUVECs) exposed to ISCLS sera with or without FX06 (50 µg/ml). Acute ISCLS serum was also tested in a three-dimensional microfluidic device. Nitric oxide (NO), VE-Cadherin localization, and cytoskeletal organization were also assessed. In two and three-dimensional systems, ISCLS sera increased endothelial permeability, with a more pronounced effect for acute sera. Furthermore, acute sera altered VE-Cadherin localization and cytoskeletal organization. NO levels remained unchanged. FX06 restored the endothelial barrier function by influencing cellular localization rather than VE-Cadherin levels. In conclusion, FX06 prevents and reverts the hyperpermeability induced by ISCLS sera. These preliminary yet promising results provide initial evidence of the in vitro efficacy of a drug targeting the underlying pathophysiological mechanisms of ISCLS. Moreover, this approach may hold potential for addressing hyperpermeability in a spectrum of clinical conditions beyond ISCLS.

Study on the Mechanism of MicroRNA551b-5p in Severe Acute Pancreatitis Capillary Leakage Syndrome.

Objective: This study focused on investigating the effects of microRNA551b-5p (miR-551b-5p) on severe acute pancreatitis. Methods: Initially, quantitative real-time polymerase chain reaction (qPCR) is employed to determine the expression of miR-551b-5p in differentiated human umbilical vein endothelial cells (HUVECs). Further, the effects of aberrantly expressed miR-551b-5p in HUVECs Transwell assay. The expressions of proteins associated with severe acute pancreatitis capillary leakage syndrome are determined by Western blot, FITC-phalloidin, and immunofluorescence stainings. Finally, the correlative factor and the target genes of miR-551b-5p, as well as their contributions, are assessed. Results: We observed that overexpression of miR-551b-5p distinctly promoted the expression of EGFR, AKT3, and AQP5, while it suppressed the expression of JAM3, AQP1, and occludin. Functionally, the cytoskeleton of the miR-551b-5p overexpression was relatively loose with apparent vacuoles, and overexpression of miR-551b-5p increased the permeability of HUVECs. Conclusion: miR-551b-5p overexpression promoted changes in vascular endothelial permeability via upregulation of the EGFR/AKT3 pathway and downregulation of occludin and JAM3.

Canagliflozin protects against sepsis capillary leak syndrome by activating endothelial α1AMPK.

Sepsis capillary leak syndrome (SCLS) is an independent prognostic factor for poor sepsis outcome. We previously demonstrated that α1AMP-activated protein kinase (α1AMPK) prevents sepsis-induced vascular hyperpermeability by mechanisms involving VE-cadherin (VE-Cad) stabilization and activation of p38 mitogen activated protein kinase/heat shock protein of 27 kDa (p38MAPK/HSP27) pathway. Canagliflozin, a sodium-glucose co-transporter 2 inhibitor, has recently been proven to activate AMPK in endothelial cells. Therefore, we hypothesized that canagliflozin could be of therapeutic potential in patients suffering from SCLS. We herein report that canagliflozin, used at clinically relevant concentrations, counteracts lipopolysaccharide-induced vascular hyperpermeability and albumin leakage in wild-type, but not in endothelial-specific α1AMPK-knockout mice. In vitro, canagliflozin was demonstrated to activate α1AMPK/p38MAPK/HSP27 pathway and to preserve VE-Cad's integrity in human endothelial cells exposed to human septic plasma. In conclusion, our data demonstrate that canagliflozin protects against SCLS via an α1AMPK-dependent pathway, and lead us to consider novel therapeutic perspectives for this drug in SCLS.

Transplant-associated thrombotic microangiopathy: Diagnostic challenges and management strategies.

Transplant-associated thrombotic microangiopathy (TA-TMA) is one of the early endothelial complications post Hematopoietic Stem Cell Transplant (HSCT). Several mechanisms during HSCT can contribute to systemic capillary endothelial damage which can lead to TA-TMA among other complications as capillary leak syndrome or engraftment syndrome. Early diagnosis of TA-TMA contributes a challenge due to overlapping clinical manifestations and the absence of specific diagnostic criteria. Incidence is greatly variable between 1-76% according to risk factors of patients and the definition used to confirm the diagnosis. The mortality rates in patients who develop severe TA-TMA are in excess of 80%. Early treatment improves the outcome. This review outlines the diagnostic challenges and therapeutic options for TA-TMA.

Whole-Exome Sequencing of Adult and Pediatric Cohorts of the Rare Vascular Disorder Systemic Capillary Leak Syndrome.

OBJECTIVE: Systemic capillary leak syndrome (SCLS) is a rare disorder that presents with episodes of hypovolemic shock. The extent to which genetic abnormalities contribute to SCLS is unknown. We identified pediatric and adult cohorts with characteristic clinical courses. We sought to describe the clinical characteristics of both cohorts, identify a possible genetic contribution to SCLS, and demonstrate that whole-exome sequencing (WES) may be conducted by critical care providers. DESIGN: Prospective observational study of WES of nine adult and eight pediatric SCLS patients and available unaffected first-degree relatives. SETTING: Tertiary children's hospitals and referral research laboratory. PATIENTS: Children and adults with SCLS. INTERVENTIONS: None. MEASUREMENTS: Patients and available first-degree relatives underwent WES. Data were analyzed for rare homozygous, biallelic, de novo, and heterozygous variants with allelic enrichment and metabolic pathway analyses. MAIN RESULTS: Children with SCLS presented at a younger age with episodes similar to those experienced by adults. All patients and available relatives underwent satisfactory WES. No overlapping gene variants or metabolic pathways were identified across all SCLS patients. Multiple candidate genes with homozygous or biallelic mutations were identified in individual subjects with SCLS. There was no significant enrichment of genes with rare heterozygous variants. CONCLUSIONS: The clinical characteristics of children and adults with SCLS are similar. We did not identify a uniform germline exomic genetic etiology for SCLS. WES identified several candidate genes in individual patients for future research. WES is a viable way for critical care providers to investigate the etiology of diseases with presumed genetic contributions.

Adrenomedullin surges are linked to acute episodes of the systemic capillary leak syndrome (Clarkson disease).

BACKGROUND: Systemic Capillary Leak Syndrome (SCLS) is an extremely rare and life-threatening vascular disorder of unknown etiology. SCLS is characterized by abrupt and transient episodes of hypotensive shock and edema due to plasma leakage into peripheral tissues. The disorder has garnered attention recently because its initial presentation resembles more common vascular disorders including systemic anaphylaxis, sepsis, and acute infections with the Ebola/Marburg family of filoviruses. Although approximately 70-85% of patients with SCLS have a concurrent monoclonal gammopathy of unknown significance (MGUS), any contribution of the paraprotein to acute flares is unknown. PROCEDURE: To identify circulating factors that might trigger acute SCLS crises, we profiled transcriptomes of paired peripheral blood mononuclear cell fractions obtained from patients during acute attacks and convalescent intervals by microarray. RESULTS: This study uncovered 61 genes that were significantly up- or downregulated more than 2.5-fold in acute samples relative to respective baselines. One of the most upregulated genes was ADM, which encodes the vasoactive peptide adrenomedullin. A stable ADM protein surrogate (pro-ADM) was markedly elevated in SCLS acute sera compared to remission samples or sera from healthy controls. Monocytes and endothelial cells (ECs) from SCLS subjects expressed significantly more ADM in response to proinflammatory stimuli compared to healthy control cells. Application of ADM to ECs elicited protective effects on vascular barrier function, suggesting a feedback protective mechanism in SCLS. CONCLUSIONS: Since ADM has established hypotensive effects, differentiating between these dual actions of ADM is crucial for therapeutic applications aimed at more common diseases associated with increased ADM levels.

Capillary leak syndrome in neuromyelitis optica treated with rituximab.

61-year-old woman with Neuromyelitis optica (NMO) diagnosis treated with rituximab was referred to our hospital with severe hypovolemic shock and anasarca. The laboratory findings showed marked hemoconcentration and a decrease in total serum protein. She developed a multiple organ failure and died three hours later. We diagnosed the patient as having capillary leak syndrome (CLS). CLS is a very rare condition caused by unexplained episodic capillary hyperpermeability, which can be idiopathic or secondary to some conditions like infection, malignant disease and some drugs like monoclonal antibodies. We reported the first CLS case in NMO patient treated with rituximab.

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.

Induction of vascular leak syndrome by tumor necrosis factor-alpha alone.

Although TNF-α possesses promising anticancer activity, clinical application is limited partly due to cardiovascular toxicities. TNF-α effects on vessels are likely related to vascular toxicity, but much remains poorly understood. Similarly, IL-2 is an attractive treatment option for cancers but its clinical use is limited by the side effect of vascular leak syndrome (VLS). We report here that TNF-α alone can trigger VLS. Administration of recombinant TNF-α induced VLS in normal mice and TNF-α transgenic mice exhibited VLS. Perivascular infiltrates in the lungs and specific cytokines in serum were observed in VLS-induced mice. This study shed a new light on the critical role of the TNF-α in IL-2-induced or non IL-2-induced VLS and provides important points to TNF-α therapy.

[Idiopathic capillary hyperpermeability syndrome revealing of Waldenström disease]. / Un syndrome d'hyperperméabilité capillaire idiopathique révélant une maladie de Waldenström.

Waldenstrom disease is a rare hematologic disorder characterized by lymphoplasmacytic proliferation associated with the production of monoclonal IgM. Visceral injuries are described but some are rare (lung), others never reported (cardiac). We report for information and discussion a case representing these particular situations, considering that these attacks were revealing. It is a 63 year old man who was admitted to the emergency room in an array of tamponade, with edema at the front and four members. Clinical and radiological examinations were objectified bilateral pleural effusion, ascite and pericarditis. The biological exploration showed pancytopenia, serum proteins 120 g/L and a monoclonal peak migrant beta2 globulin electrophoresis which is made by monoclonal immunoglobulin M (IgM kappa). The bone marrow confirmed the diagnosis of the Waldenström disease. This is a mode of revelation never described before. Considering this case, it would be wise to think of a Waldenström disease before any polyserositis.

Early prediction of capillary leak syndrome in infants after cardiopulmonary bypass.

OBJECTIVES: As an inflammatory reaction after cardiac surgery involving cardiopulmonary bypass (CPB), capillary leak syndrome (CLS) is associated with increased morbidity, especially in newborns and infants. We investigated whether different cytokines measured via microdialysis can monitor local inflammation in adipose tissue subcutaneously and predict the development of CLS early, before clinical signs appear. Furthermore, we investigated whether there are age-related differences between the inflammatory responses in newborns and infants. METHODS: We performed a prospective study taking serial measurements of the inflammatory response detected in subcutaneous adipose tissue up to 24 h postoperatively. The cohort consisted of 23 neonates and infants (median age 155, range 6-352 days; median body weight 5.4 kg, range 2.6-9.2 kg) who underwent congenital heart surgery with CPB. Microdialysis catheters were introduced in one lateral thigh subcutaneously using a velocity of 1.0 µl/min. Serial microdialysis analyses for cytokines (interleukin [IL]-6, IL-8, IL-10) and complement activation (C3a) were performed. CLS was quantified by X-ray subcutaneous-thoracic ratios. RESULTS: The median bypass time was 150 min (range 42-432 min) and the aortic cross-clamp time 76 min (range 0-188 min). Six out of 23 infants developed postoperative CLS. Younger age (P = 0.02) and longer bypass time (r = 0.48; P = 0.021) correlated strongly with the development of CLS. Pro- and anti-inflammatory cytokines and complement activation were detected subcutaneously in all patients. The highest levels of IL-6 (55.0 pg/ml) and IL-8 (65.9 pg/ml) were detected 2 h after CPB. During surgery, the C3a level rose dramatically (167.1 ng/ml), followed by a release of IL-10 at the end of CPB. Patients with CLS produced a characteristic and significant second peak of C3a at 8 h postoperatively (CLS 63.8 ng/ml vs non-CLS 23.5 ng/ml; P < 0.01). We detected an aged-related difference in the release of IL-6 and C3a. Longer intubation time (r = 0.63; P = 0.001), higher inotropic demand (r = 0.67; P = 0.001) and higher serological lactate levels (r = 0.65; P = 0.001) correlated closely with the development of CLS. CONCLUSION: Diagnostic microdialysis can detect local inflammation and may predict the development of CLS early before severe clinical signs appear.

Interleukin-6 in sepsis and capillary leakage syndrome.

Bacterial sepsis is one of the most frequent and dreaded causes of death in intensive care units. According to the current understanding of sepsis, bacterial components activate innate immune responses via pattern-recognition receptors that stimulate signaling pathways, thereby leading to activation of NF-κB and the release of cytokines, alarming the organism and coordinating appropriate defense mechanisms. The resulting "cytokine storm" not only restricts bacterial invasion; it also harms the host by triggering a hemodynamic collapse with a drop in blood pressure, which could lead to death. One of the cytokines released during sepsis is interleukin-6 (IL-6). Originally described as a B-cell-stimulating factor, this cytokine has since been shown to have multiple additional functions. Interestingly, there is emerging evidence of IL-6 trans-signaling in the pathogenesis of sepsis. We review recent findings and discuss whether therapeutic interference with IL-6 trans-signaling may be beneficial in this important clinical scenario.

Splenectomy exacerbates lung injury after ischemic acute kidney injury in mice.

Patients with acute kidney injury (AKI) have increased serum proinflammatory cytokines and an increased occurrence of respiratory complications. The aim of the present study was to examine the effect of renal and extrarenal cytokine production on AKI-mediated lung injury in mice. C57Bl/6 mice underwent sham surgery, splenectomy, ischemic AKI, or ischemic AKI with splenectomy and kidney, spleen, and liver cytokine mRNA, serum cytokines, and lung injury were examined. The proinflammatory cytokines IL-6, CXCL1, IL-1ß, and TNF-α were increased in the kidney, spleen, and liver within 6 h of ischemic AKI. Since splenic proinflammatory cytokines were increased, we hypothesized that splenectomy would protect against AKI-mediated lung injury. On the contrary, splenectomy with AKI resulted in increased serum IL-6 and worse lung injury as judged by increased lung capillary leak, higher lung myeloperoxidase activity, and higher lung CXCL1 vs. AKI alone. Splenectomy itself was not associated with increased serum IL-6 or lung injury vs. sham. To investigate the mechanism of the increased proinflammatory response, splenic production of the anti-inflammatory cytokine IL-10 was determined and was markedly upregulated. To confirm that splenic IL-10 downregulates the proinflammatory response of AKI, IL-10 was administered to splenectomized mice with AKI, which reduced serum IL-6 and improved lung injury. Our data demonstrate that AKI in the absence of a counter anti-inflammatory response by splenic IL-10 production results in an exuberant proinflammatory response and lung injury.

Endothelial nitric oxide synthase is a key mediator of interleukin-2-induced hypotension and vascular leak syndrome.

Despite increasing use of "targeted therapy," interleukin-2 (IL-2) is unique, because this cytokine can induce long-term remissions in 5% to 7% of patients with metastatic melanoma and renal cancer. Clinical use of IL-2 is limited by severe toxicities, such as hypotension and vascular leak syndrome (VLS). Nitric oxide seems to be involved in the pathogenesis of these toxicities. On the basis of previous studies, we hypothesized that the endothelial nitric oxide synthase (eNOS) is the major source of nitric oxide. Mice with a knockout of the eNOS isoenzyme were treated with IL-2 (800,000 IU twice daily for 5 d). Blood pressure and vascular leak were measured. Inhibitors of superoxide, nitric oxide, and soluble guanylate cyclase were used to probe the mechanism. These experiments showed that IL-2 treatment increased eNOS messenger ribonucleic acid expression and nitric oxide metabolite excretion in eNOS knockout mice. Unlike normal and inducible nitric oxide synthase knockout mice, eNOS knockout mice proved resistant to IL-2-induced hypotension and vascular leak. Although hypotension seems to be mediated by superoxide or peroxynitrite, vascular leak seemed to be mediated by nitric oxide. Inhibition of guanylate cyclase and cyclic guanylate monophosphate formation during IL-2 treatment using methylene blue (MB)-inhibited vascular leak. MB treatment did not interfere with IL-2-induced antitumor mechanisms. Our experiments established that eNOS is a key mediator of IL-2-induced VLS and hypotension. A clinical trial of MB infusion during IL-2 therapy is currently being planned.

The role of the endothelium in the short-term complications of hematopoietic SCT.

In this review, we analyse the role of the endothelium in the development of several complications that appear soon after haematopoietic SCT (HSCT). Once it had been demonstrated that sinusoidal damage is the initiating event of the sinusoidal obstruction syndrome, it was considered that other short-term complications with overlapping clinical manifestations, such as capillary leak syndrome, engraftment syndrome, transplant-associated microangiopathy, diffuse alveolar haemorrhage and idiopathic pneumonia syndrome, could have an endothelial origin. During HSCT, endothelial cells (ECs) are activated and damaged by several factors, including conditioning, cytokines released by damaged tissues, endotoxins translocated through damaged mucosa, drugs used in the procedure, the engraftment, and--in the allogeneic setting--immunological reactions. The different clinical syndromes that occur could be determined by the predominant phenotypic change in the ECs and the location of this change (organ dependant or systemic). Several translational studies have provided evidence of this endothelial dysfunction on the basis of analysis of soluble markers, soluble forms of adhesion molecules, the enumeration of circulating ECs and microparticles, and morphologic and functional changes induced in cultured ECs. This increased knowledge has opened up a wide range of potential pharmacologic interventions to prevent or treat endothelial damage and, consequently, to improve the outcome of patients receiving HSCT.

Transgenic myocardial overexpression of prokineticin receptor-2 (GPR73b) induces hypertrophy and capillary vessel leakage.

AIMS: Prokineticins are small secreted bioactive molecules. They exert their biological activity by binding to two G protein-coupled receptors. Previously, we have shown that the overexpression of prokineticin receptor-1 (PKR1) in transgenic (TG) mouse hearts induced neovascularization. Since PKR1 and PKR2 are 85% identical and expressed in cardiovascular tissues, we hypothesized that PKR2 may also contribute to cardiomyocyte growth and vascularization. METHODS AND RESULTS: We have generated TG mice overexpressing PKR2 in cardiomyocytes. TG mice exhibit increased hypertrophic gene expression and heart-to-body weight ratio accompanied by an increased length of cardiomyocytes at the age of 12 weeks. Increased left ventricular end-systolic and diastolic diameters without cardiac dysfunction at the age of 24 weeks indicate that TG mice have an eccentric hypertrophy with compensated cardiac function. Quantitative morphological analysis showed that TG hearts have a normal microvessel density and number of branch points. However, they exhibit increased abnormal endothelial cell shape and ultrastructure, changed cellular distribution of a tight junction protein zona occludens-1 (ZO-1), and vascular leakage in heart without a rise of angiogenic factor levels at early and late age. The application of media conditioned by H9c2 cardioblast cells overexpressing PKR2 significantly induced impaired ZO-1 localization in H5V endothelial cells, mimicking the TG model. CONCLUSION: These findings provide the first genetic evidence that cardiomyocyte PKR2 signalling leads to eccentric hypertrophy in an autocrine regulation and impaired endothelial integrity in a paracrine regulation without inducing angiogenesis. These TG mice may provide a new genetic model for heart diseases.

Inhibitory effect of dimethylthiourea on rat urinary bladder inflammation produced by 6-hydroxydopamine application.

The present study was to investigate 6-hydroxydopamine (6-OHDA)-induced inflammatory response and underlying mechanisms in the urinary bladder in anesthetized male rats of Long-Evans strain. The magnitude of inflammation was evaluated by morphometric analysis of the relative number of leaky blood vessels expressed by the area density of India ink-labeled blood vessels in whole mount specimens. Light and scanning electron microscopies were employed to study the changes in histologic structure and endothelial ultrastructure of bladder wall. Local injection of 6-OHDA to lumen of urinary bladder induced a dose-dependent increase in plasma leakage. Following application of vehicle, 5 mg/kg 6-OHDA, and 10 mg/kg 6-OHDA, area densities of India ink-labeled leaky vessels were 5.65+/-3.72% (N=6), 22.63+/-5.12% (N=6), and 35.02+/-11.25% (N=6), respectively. Inflammatory response was completely abolished by pretreatment alone with dimethylthiourea (DMTU), a hydroxyl radical scavenger, and was also attenuated by pretreatment with L-732,138, a NK1 receptor antagonist. 6-OHDA caused edema formation and venular endothelial gap formation in bladder tissue. It is concluded that 6-OHDA induced inflammation in the rat urinary bladder, the response of which was dose-dependently increased and free radicals and tachykinins were involved in the inflammatory process.