Contribution of ADAMTS13‐independent VWF regulation in sickle cell disease

Abstract

Background: Von Willebrand factor (VWF) is elevated in sickle cell disease (SCD) and contributes to vaso-occlusion through its thrombogenic properties. VWF is regulated by ADAMTS13, a plasma protease that cleaves VWF into less bioactive multimers.Independent investigations have shown VWF to be elevated in SCD, whereas measurements of ADAMTS13 have been variable. Objectives:We assessed ADAMTS13 activity using multiple activity assays and measured levels of alternative VWF-cleaving proteases in SCD. Methods/ Patients: Plasma samples were collected from adult patients with SCD (n = 20) at a single institution when presenting for routine red cell exchange transfusion therapy. ADAMTS13 activity was measured by FRETS-VWF73, Technozym ADAMTS-13 Activity ELISA kit and a full-length VWF digestion reaction. Alternative VWF-cleaving proteases were identified by ELISA. A cell culture model was used to study the impact of SCD stimuli on endothelial ADAMTS13 and alternative VWFcleaving proteases.Results: ADAMTS13 activity was found to be moderately deficient across the SCD cohort as assessed by activity assays using a VWF A2 domain peptide substrate. However, SCD plasma showed preserved ability to digest full-length VWF, suggesting assay-discrepant results. Neutrophil and endothelial-derived proteases were found to be elevated in SCD plasma. Matrix metalloproteinase 9 specifically showed preferential cleavage of full-length VWF. Upregulation of alternative VWF-cleaving proteases occurred in endothelial cells exposed to SCD stimuli such as heme and hypoxia.Conclusions: This is the first demonstration of accessory plasma enzymes contributing to the regulation of VWF in a specific disease state and may have implications for assessing the VWF/ADAMTS13 axis in other settings.

Hidden behind thromboinflammation: revealing the roles of von Willebrand factor in sickle cell disease pathophysiology

“…Although there still remain gaps in our general understanding of the factors that dysregulate this pathway, particularly with respect to ADAMTS13 inhibition, as studies have recently reported additional inhibitory mechanisms. While there exists ADAMTS13-independent proteolytic pathways that increase in SCD patients to regulate VWF, such as neutrophil and endothelial-derived proteases and matrix metalloproteinase 9, their activity is not sufficient in mitigating the VWF burden in SCD [ 28 ▪▪ ]. Notably, studies have demonstrated that the gold standard treatment for SCD, hydroxyurea, does not prevent the dysregulation of the VWF - ADAMTS13 axis in SCD, leaving patients still susceptible to its downstream complications [ 29 ▪ ].…”

The invisible string of coagulation, complement, iron, and inflammation in sickle cell disease

“…ADAMTS-13 independent cleavage of VWF has also been found in SCD patient plasma [55], opening the possibility that other proteases, such as matrix metallopeptidase 9, could play a role in VWF processing.…”

“…A double-blind, placebo-controlled, phase I clinical trial, called rADAMST-13 in Sickle Cell Disease (RAISE), is enrolling adult SCD patients (NCT 03997760) and will investigate the effect of rADAMTS13 on disease severity markers. ADAMTS-13 independent cleavage of VWF has also been found in SCD patient plasma [55], opening the possibility that other proteases, such as matrix metallopeptidase 9, could play a role in VWF processing.…”

Differential expression of adhesion molecules in sickle cell anemia and gut microbiome effect

“…Usually, the number of acute episodes tends to increase with age, and more than 50% of adults with SCD suffer from persistent chronic pain [ 11 ]. Leukocyte activation, oxidative stress, and ischemia/reperfusion are some factors specific to SCD that can trigger endothelial activation and lead to the development of VOC episodes [ 12 ]. Following the endothelial activation, nitric oxide bioavailability is impaired, and a variety of endothelial adhesion molecules are expressed (e.g., VCAM-1, selectins, ICAM-1), which will affect both the macro- and microvasculature [ 12 , 13 ].…”

“…Leukocyte activation, oxidative stress, and ischemia/reperfusion are some factors specific to SCD that can trigger endothelial activation and lead to the development of VOC episodes [ 12 ]. Following the endothelial activation, nitric oxide bioavailability is impaired, and a variety of endothelial adhesion molecules are expressed (e.g., VCAM-1, selectins, ICAM-1), which will affect both the macro- and microvasculature [ 12 , 13 ]. Even at steady state, SCD subjects have elevated levels of these adhesion molecules compared with controls, and it was reported a further increase during VOC episodes, suggesting a key involvement [ 4 , 6 , 10 ].…”