Reduction of mortality, cardiac damage, and cerebral damage by IL-1 inhibition in a murine model of TTP.

ABSTRACT: Thrombotic thrombocytopenic purpura (TTP), a rare but fatal disease if untreated, is due to alteration in von Willebrand factor cleavage resulting in capillary microthrombus formation and ischemic organ damage. Interleukin-1 (IL-1) has been shown to drive sterile inflammation after ischemia and could play an essential contribution to postischemic organ damage in TTP. Our objectives were to evaluate IL-1 involvement during TTP and to test the efficacy of the recombinant IL-1 receptor antagonist, anakinra, in a murine TTP model. We retrospectively measured plasma IL-1 concentrations in patients with TTP and controls. Patients with TTP exhibited elevated plasma IL-1α and -1ß concentrations, which correlated with disease course and survival. In a mouse model of TTP, we administered anakinra (IL-1 inhibitor) or placebo for 5 days and evaluated the efficacy of this treatment. Anakinra significantly reduced mortality of mice (P < .001). Anakinra significantly decreased TTP-induced cardiac damage as assessed by blood troponin concentrations, evaluation of left ventricular function by echocardiography, [18F]fluorodeoxyglucose positron emission tomography of myocardial glucose metabolism, and cardiac histology. Anakinra also significantly reduced brain TTP-induced damage evaluated through blood PS100b concentrations, nuclear imaging, and histology. We finally showed that IL-1α and -1ß trigger endothelial degranulation in vitro, leading to the release of von Willebrand factor. In conclusion, anakinra significantly reduced TTP mortality in a preclinical model of the disease by inhibiting both endothelial degranulation and postischemic inflammation, supporting further evaluations in humans.

Circulating endothelial cells in pathophysiology.

PURPOSE OF REVIEW: The purpose of this review is to synthesize recent insights into the roles and importance of circulating endothelial cells (CECs) as indicators of the severity, progression, and prognosis of vascular-related diseases. RECENT FINDINGS: Recent studies have identified elevated counts of CECs in pathological conditions, notably inflammatory or cardiovascular diseases such as acute myocardial infarction and heart failure, underscoring their potential as sensitive indicators of disease. Furthermore, the rise in CEC levels in cancer patients, particularly with disease advancement, points to their role in cancer-associated angiogenesis and response to treatment. SUMMARY: This review underscores the evolving significance of CECs as markers for evaluating the gravity and advancement of diseases with vascular injury, including cardiovascular diseases, cancer, inflammatory conditions, and thromboembolic events. These last years, efforts made to standardize flow cytometry detection of CEC and the development of highly sensitive techniques to isolate, quantify or phenotype rare cells open promising avenues for clinical application. This may yield extensive knowledge regarding the mechanisms by which endothelial cells contribute to a variety of vascular-related disorders and their clinical value as emerging biomarkers.

Vascular endothelial-cadherin is involved in endothelial cell detachment during thrombotic thrombocytopenic purpura.

BACKGROUND: Immune thrombotic thrombocytopenic purpura (i-TTP) is a life-threatening thrombotic microangiopathy linked to ADAMTS-13 deficiency. It has long been assumed that the activation of endothelial cells is the triggering factor for the thrombotic thrombocytopenic purpura crisis. Circulating endothelial cells (CECs) have been shown to be a biomarker of vascular damage and are associated with the clinical severity of i-TTP. However, the mechanisms leading to endothelial cell detachment remain unclear. OBJECTIVES: We investigated junctional destabilization the mechanisms underlying cell detachment in thrombotic thrombocytopenic purpura. METHODS: We quantified CECs in i-TTP patients and investigated the effect of plasmas in vitro by measuring phosphorylation and internalization of vascular endothelial (VE)-Cadherin and in vivo in a vascular permeability model. RESULTS: In plasma from i-TTP patients, we show that CEC count is associated with severity and correlated to intracellular calcium influx (P < .01). In vitro, serum from i-TTP patients induced stronger detachment of human umbilical vein endothelial cells than serum from control patients (P < .001). Plasma from i-TTP patients induced a higher calcium-dependent phosphorylation (P < .05) and internalization (P < .05) of VE-cadherin compared with plasma from control patients. This effect could be reproduced by immunoglobulin (Ig)G fraction isolated from patient plasma and, in particular, by the F(ab)'2 fragments of the corresponding IgG. In addition, subcutaneous injection of i-TTP plasma into mice resulted in higher vascular permeability than plasma from control patients. An inhibitor of endothelial calcium influx, ITF1697, normalized this increase in permeability. CONCLUSION: Our results suggest that plasma-induced endothelial activation also leads to an increase in vascular permeability. They contribute to the understanding of the mechanisms behind the presence of elevated CECs in patients' blood by linking endothelial activation to endothelial injury.

Comparison of assays measuring extracellular vesicle tissue factor in plasma samples: communication from the ISTH SSC Subcommittee on Vascular Biology.

BACKGROUND: Scientific and clinical interest in extracellular vesicles (EVs) is growing. EVs that expose tissue factor (TF) bind factor VII/VIIa and can trigger coagulation. Highly procoagulant TF-exposing EVs are detectable in the circulation in various diseases, such as sepsis, COVID-19, or cancer. Many in-house and commercially available assays have been developed to measure EV-TF activity and antigen, but only a few studies have compared some of these assays. OBJECTIVES: The International Society on Thrombosis and Haemostasis Scientific and Standardization Committee Subcommittee on Vascular Biology initiated a multicenter study to compare the sensitivity, specificity, and reproducibility of these assays. METHODS: Platelet-depleted plasma samples were prepared from blood of healthy donors. The plasma samples were spiked either with EVs from human milk or EVs from TF-positive and TF-negative cell lines. Plasma was also prepared from whole human blood with or without lipopolysaccharide stimulation. Twenty-one laboratories measured EV-TF activity and antigen in the prepared samples using their own assays representing 18 functional and 9 antigenic assays. RESULTS: There was a large variability in the absolute values for the different EV-TF activity and antigen assays. Activity assays had higher specificity and sensitivity compared with antigen assays. In addition, there was a large intra-assay and interassay variability. Functional assays that used a blocking anti-TF antibody or immunocapture were the most specific and sensitive. Activity assays that used immunocapture had a lower coefficient of variation compared with assays that isolated EVs by high-speed centrifugation. CONCLUSION: Based on this multicenter study, we recommend measuring EV-TF using a functional assay in the presence of an anti-TF antibody.