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.

Markers of endothelial glycocalyx dysfunction in Clarkson disease.

BACKGROUND: Clarkson disease (monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome, ISCLS) is a rare idiopathic condition marked by transient, relapsing-remitting episodes of systemic microvascular hyper-permeability, which liberates plasma fluid and macromolecules into the peripheral tissues. This pathology manifests clinically as the abrupt onset of hypotensive shock, hemoconcentration, and hypoalbuminemia. METHODS: We analysed endothelial glycocalyx (eGCX)-related markers in plasma from patients with ISCLS during acute disease flares and convalescence by ELISA and comprehensive proteomic profiling. We evaluated eGCX-related components and gene expression in cultured endothelial cells using RNA-sequencing, real-time PCR, and fluorescence staining. RESULTS: Serum levels of eGCX-related core components including hyaluronic acid (HA) and the core proteoglycan soluble syndecan-1 (sCD138) were elevated at baseline and during acute ISCLS flares. Serial measurements demonstrated that sCD138 levels peaked during the recovery (post-leak) phase of the illness. Proteomic analysis of matched acute and convalescent ISCLS plasma revealed increased abundance of eGCX-related proteins, including glypicans, thrombospondin-1 (TSP-1), and eGCX-degrading enzymes in acute compared to remission plasma. Abundance of endothelial cell damage markers did not differ in acute and baseline plasma. Expression of several eGCX-related genes and surface carbohydrate content in endothelial cells from patients with ISCLS did not differ significantly from that observed in healthy control cells. CONCLUSIONS: eGCX dysfunction, but not endothelial injury, may contribute to clinical symptoms of acute ISCLS. Serum levels of of eGCX components including sCD138 may be measured during acute episodes of ISCLS to monitor clinical status and therapeutic responses.

A case of chronic systemic capillary leak syndrome (SCLS) exacerbated during SARS-CoV2 infection.

Systemic capillary leak syndrome (SCLS) is a very rare and lethal disease characterized by hemoconcentration and hypoalbuminemia caused by reversible plasma extravasation. The underlying cause for SCLS remains largely unknown and acute treatment has remained mainly supportive. Prophylaxis with intravenous immunoglobulin (IVIG) has been shown to successfully prevent further episodes in affected patients. We reported a case of SCLS in a patient who presented to our hospital with COVID-19 and developed profound shock.

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.

Immunotoxin SS1P is rapidly removed by proximal tubule cells of kidney, whose damage contributes to albumin loss in urine.

Recombinant immunotoxins (RITs) are chimeric proteins composed of an Fv and a protein toxin being developed for cancer treatment. The Fv brings the toxin to the cancer cell, but most of the RITs do not reach the tumor and are removed by other organs. To identify cells responsible for RIT removal, and the pathway by which RITs reach these cells, we studied SS1P, a 63-kDa RIT that targets mesothelin-expressing tumors and has a short serum half-life. The major organs that remove RIT were identified by live mouse imaging of RIT labeled with FNIR-Z-759. Cells responsible for SS1P removal were identified by immunohistochemistry and intravital two-photon microscopy of kidneys of rats. The primary organ of SS1P removal is kidney followed by liver. In the kidney, SS1P passes through the glomerulus, is taken up by proximal tubular cells, and transferred to lysosomes. In the liver, macrophages are involved in removal. The short half-life of SS1P is due to its very rapid filtration by the kidney followed by degradation in proximal tubular cells of the kidney. In mice treated with SS1P, proximal tubular cells are damaged and albumin in the urine is increased. SS1P uptake by kidney is reduced by coadministration of l-lysine. Our data suggests that l-lysine administration to humans might prevent SS1P-mediated kidney damage, reduce albumin loss in urine, and alleviate capillary leak syndrome.

Neutrophil activation in systemic capillary leak syndrome (Clarkson disease).

Systemic capillary leak syndrome (SCLS; Clarkson disease) is a rare orphan disorder characterized by transient yet recurrent episodes of hypotension and peripheral oedema due to diffuse vascular leakage of fluids and proteins into soft tissues. Humoral mediators, cellular responses and genetic features accounting for the clinical phenotype of SCLS are virtually unknown. Here, we searched for factors altered in acute SCLS plasma relative to matched convalescent samples using multiplexed aptamer-based proteomic screening. Relative amounts of 612 proteins were changed greater than twofold and 81 proteins were changed at least threefold. Among the most enriched proteins in acute SCLS plasma were neutrophil granule components including bactericidal permeability inducing protein, myeloperoxidase and matrix metalloproteinase 8. Neutrophils isolated from blood of subjects with SCLS or healthy controls responded similarly to routine pro-inflammatory mediators. However, acute SCLS sera activated neutrophils relative to remission sera. Activated neutrophil supernatants increased permeability of endothelial cells from both controls and SCLS subjects equivalently. Our results suggest systemic neutrophil degranulation during SCLS acute flares, which may contribute to the clinical manifestations of acute vascular leak.

A pericyte-glia scarring develops at the leaky capillaries in the hippocampus during seizure activity.

OBJECTIVE: Inflammatory cerebrovascular damage occurs in epilepsy. Here, we tested the hypothesis that a pericyte-glia scar forms around the outer wall of hippocampal capillaries in a model of temporal lobe epilepsy associated with hippocampal sclerosis. We studied the participation of stromal cells expressing platelet-derived growth factor receptor beta (PDGFRß) and extracellular matrix modifications to the perivascular scar during epileptogenesis. METHODS: We used NG2DsRed/C57BL6 mice and induced status epilepticus (SE) followed by epileptogenesis and spontaneous recurrent seizures (SRS) by means of unilateral intrahippocampal injection of kainic acid (KA). For pharmacological assessment, we used organotypic hippocampal cultures (OHCs) where ictal electrographic activity was elicited by KA or bicuculline. RESULTS: NG2DsRed pericytes, GFAP astroglia, and IBA1 microglia are reactive and converge to form a pericapillary multicellular scar in the CA hippocampal regions during epileptogenesis and at SRS. The capillaries are leaky as indicated by fluorescein entering the parenchyma from the peripheral blood. Concomitantly, PDGFRß transcript and protein levels were significantly increased. Within the regional scar, a fibrotic-like PDGFRß mesh developed around the capillaries, peaking at 1 week post-SE and regressing, but not resolving, at SRS. Abnormal distribution or accumulation of extracellular matrix collagens III/IV occurred in the CA regions during seizure progression. PDGFRß/DAPI cells were in direct contact with or adjacent to the damaged NG2DsRed pericytes at the capillary interface, consistent with the notion of stromal cell reactivity or fibroblast formation. Inducing electrographic activity in OHCs was sufficient to augment PDGFRß reactivity around the capillaries. The latter effect was pharmacologically mimicked by treating OHCs with the PDGFRß agonist PDGF-BB and it was diminished by the PDGFRß inhibitor imatinib. SIGNIFICANCE: The reported multicellular activation and scar are traits of perivascular inflammation and hippocampal sclerosis in experimental epilepsy, with an implication for neurovascular dysfunction. Modulation of PDGFRß could be exploited to target inflammation in this chronic disease setting.

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.

Probable Mechanisms Involved in Immunotoxin Mediated Capillary Leak Syndrome (CLS) and Recently Developed Countering Strategies.

Antibody-toxin fused agents or immunotoxins, are a newly engineered class of cytotoxic agents consisting of a bacterial or plant toxin moiety hooked up either to a monoclonal antibody or a specific growth factor. Nevertheless, acquiring a full potency in clinic is mostly restricted due to the Capillary leak syndrome (CLS), a serious immune provoked, life-threatening side effect, subsequent to the endothelial damage, resulting in fluid escape from the bloodstream into tissues including lungs, muscle and brain, developing organ failure and eventually death. Proposed underlying mechanisms include direct damage to endothelial cells, acute inflammation, Lymphokine-activated killer (LAK) cells engagement, alteration in cell-cell/cell-matrix connectivities and cytoskeletal dysfunction. Very poor biodistribution and heterogeneous extravasation pattern in tumor site result in accumulation of ITs close to the extravasation site, gradual toxin release and initiation of nearby endothelial cells lysis, secretion of pro-inflammatory cytokines, development of acute inflammation and engagement of Lymphokine-activated killer (LAK) cells. Intrinsic immunogenicity of applied toxin moiety is another important determinant of CLS incidence. Toxins with more intrinsic immunogenicity possess more probability for CLS development. Recently, development of new generations of antibodies and mutated toxins with conserved cytotoxicity has partly tapered risk of CLS development. Here, we describe probable mechanisms involved in CLS and introduce some of the recently applied strategies for lessening incidence of CLS as much as possible.

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.

How relevant are vascular endothelial growth factor and intercellular adhesion molecule in the systemic capillary leak syndrome of psoriasis?

Abstract: Psoriasis is a chronic disease, characterized by erythematous scaly lesions, presented in eight different forms: plaques, guttate, pustular, erythrodermic, inverse, nail and scalp psoriasis, and psoriatic arthritis. Its development depends on genetic factors, external stimulus and immune response alteration.1 Proinflammatory cytokines such as TNF-alpha, IL-12 and 23 may also be involved. In the worst cases, systemic complications linked to endothelial alterations may occur. A literature review was conducted for a better understanding of what roles VEGF (vascular endothelial growth factor) and ICAM-1 (intercellular adhesion molecule) have, among other cytokines, in systemic capillary leak syndrome, involved in erythrodermic and pustular psoriasis, the most unstable forms of the disease.

A p190BRhoGAP mutation and prolonged RhoB activation in fatal systemic capillary leak syndrome.

We describe a fatal case of pediatric systemic capillary leak (Clarkson's disease) associated with a point mutation in p190BRhoGAP. Dermal microvascular endothelial cells (ECs) isolated from this patient form monolayers with similar levels and distribution of junctional proteins and transendothelial electrical resistance compared with normal human dermal microvascular ECs. However, patient-derived ECs demonstrate a greater increase in permeability and impaired recovery of barrier function in response to tumor necrosis factor (TNF) compared with normal donor EC cultures. TNF transiently activates RhoB in ECs coincident with developing leak, and inactivation of RhoB correlates with barrier recovery. The mutation in p190BRhoGAP impairs RhoB inactivation, and the mutant phenotype of patient-derived ECs is replicated by siRNA knockdown of p190BRhoGAP in normal ECs. These data suggest a previously unknown function for p190BRhoGAP in control of capillary EC barrier function that may also be important in acquired systemic capillary leak associated with critical illness in humans.

Intravenous Immunoglobulins Improve Survival in Monoclonal Gammopathy-Associated Systemic Capillary-Leak Syndrome.

BACKGROUND: Monoclonal gammopathy-associated systemic capillary-leak syndrome, also known as Clarkson disease, is a rare condition characterized by recurrent life-threatening episodes of capillary hyperpermeability in the context of a monoclonal gammopathy. This study was conducted to better describe the clinical characteristics, natural history, and long-term outcome of monoclonal gammopathy-associated systemic capillary-leak syndrome. METHODS: We conducted a cohort analysis of all patients included in the European Clarkson disease (EurêClark) registry between January 1997 and March 2016. From diagnosis to last follow-up, studied outcomes (eg, the frequency and severity of attacks, death, and evolution toward multiple myeloma) and the type of preventive treatments administered were monitored every 6 months. RESULTS: Sixty-nine patients (M/F sex ratio 1:1; mean ± SD age at disease onset 52 ± 12 years) were included in the study. All patients had monoclonal gammopathy of immunoglobulin G type, with kappa light chains in 47 (68%). Median (interquartile range) follow-up duration was 5.1 (2.5-9.7) years. Twenty-four patients (35%) died after 3.3 (0.9-8) years. Fifty-seven (86%) patients received at least one preventive treatment, including intravenous immunoglobulins (IVIg) n = 48 (73.8%), theophylline n = 22 (33.8%), terbutaline n = 22 (33.8%), and thalidomide n = 5 (7.7%). In the 65 patients with follow-up, 5- and 10-year survival rates were 78% (n = 35) and 69% (n = 17), respectively. Multivariate analysis found preventive treatment with IVIg (hazard ratio 0.27; 95% confidence interval, 0.10-0.70; P = .007) and terbutaline (hazard ratio 0.35; 95% confidence interval, 0.13-0.96; P = .041) to be independent predictors of mortality. CONCLUSIONS: We describe the largest cohort to date of patients with well-defined monoclonal gammopathy-associated systemic capillary-leak syndrome. Preventive treatment with IVIg was the strongest factor associated with survival, suggesting the use of IVIg as the first line in prevention therapy.

How relevant are vascular endothelial growth factor and intercellular adhesion molecule in the systemic capillary leak syndrome of psoriasis?

Psoriasis is a chronic disease, characterized by erythematous scaly lesions, presented in eight different forms: plaques, guttate, pustular, erythrodermic, inverse, nail and scalp psoriasis, and psoriatic arthritis. Its development depends on genetic factors, external stimulus and immune response alteration.1 Proinflammatory cytokines such as TNF-alpha, IL-12 and 23 may also be involved. In the worst cases, systemic complications linked to endothelial alterations may occur. A literature review was conducted for a better understanding of what roles VEGF (vascular endothelial growth factor) and ICAM-1 (intercellular adhesion molecule) have, among other cytokines, in systemic capillary leak syndrome, involved in erythrodermic and pustular psoriasis, the most unstable forms of the disease.

A Case of Refractory Systemic Capillary Leak Syndrome (Clarkson's Disease) during Pregnancy.

A 32-year-old woman, pregnant with twins, presented with a chief complaint of general fatigue. Her general condition had rapidly deteriorated since her last visit to the primary obstetrician; the patient was then referred to our hospital because of suspected fetal death. She underwent emergency cesarean section because fetal death had indeed occurred, and she was then admitted to the intensive care unit (ICU). On ICU admission, she was found to be in shock. Laboratory analysis revealed extreme hemoconcentration and a low albumin level, and initially, septic shock with obstetric complications was suspected. However, because she did not respond to conventional therapy but instead, rapidly developed severe generalized edema, systemic capillary leak syndrome (SCLS) was diagnosed. The patient remained in shock for several days until undergoing plasma exchange (PE), despite some earlier empirical treatments. She eventually recovered from profound shock status and was discharged from the ICU without sequelae. Among potentially effective treatments, PE seemed to be the most reasonable choice for the treatment of her SCLS.