Biology subjects

Constantinescu-Bercu, A.

Publications and source records attributed to Constantinescu-Bercu, A..

3 recordsLinked to original sources

bioRxiv2025

Von Willebrand Factor Deficiency Impairs Vascular Morphogenesis via Angiopoietin-2: Relevance for Gut Angiodysplasia

Management of recurrent gastrointestinal (GI) bleeding is a clinical unmet need for patients with Von Willebrand disease (VWD) and is linked to the presence of gut vascular malformations (angiodysplasia). We previously demonstrated that von Willebrand factor (VWF) regulates angiogenesis and vascular integrity, the likely mechanism underlying angiodysplasia. VWF controls the storage of the angiogenesis regulator Angiopoietin-2 (Angpt-2) in endothelial cells (EC), suggesting a candidate for the genesis of angiodysplasia; however, no direct evidence of the role of Angpt-2 in VWF-dependent angiogenesis is available. Here we use VWF-deficient HUVEC, and endothelial colony forming cells (ECFCs) from severe VWD patients and find that loss of VWF in EC results in increased Angpt-2 expression through a positive feedback loop via the Angpt-2-TIE2-AKT-FOXO1 pathway. We also show an imbalance of the Angpt/Tie2 pathway in vivo. In the gut of VWF-deficient mice, Angpt-2 expression is increased whilst Angpt-1 expression is decreased; this correlates with reduced expression of the pericyte marker NG2. These data suggest that VWF regulates the Angpt/Tie2 balance in the gut. To investigate the functional defects caused by loss of VWF, we use a fibrin bead assay and show that VWF-deficient HUVEC present increased sprouting. We develop a microfluidic model of 3D vasculogenesis/angiogenesis and find that ECFCs from VWD patients exhibit defective remodeling and abnormal lumen formation compared to healthy controls. Importantly, inhibition of Angpt-2 reduces sprouting in VWF-deficient HUVEC and normalises vascular networks in ECFCs from severe VWD, suggesting Angpt-2 inhibitors may be effective in VWD patients with GI bleeding and angiodysplasia. Key pointsO_LIEndothelial VWF regulates multiple steps of angiogenesis, including sprouting and lumen formation. C_LIO_LIVWF regulates Angpt-2 storage and expression, and Angpt-2 blockade normalises defective angiogenesis in VWD ECFCs. C_LI Visual Abstract O_FIG O_LINKSMALLFIG WIDTH=170 HEIGHT=200 SRC="FIGDIR/small/675051v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@150eb15org.highwire.dtl.DTLVardef@179e6beorg.highwire.dtl.DTLVardef@1bcadborg.highwire.dtl.DTLVardef@a30fb8_HPS_FORMAT_FIGEXP M_FIG VWF deficiency in HUVECs results in increased Angpt-2 release and expression via the Tie2-Akt-FOXO1 pathway. A. Model pathway for the regulation of Angpt-2 levels by VWF. Loss of VWF results in increased Angpt-2 release from endothelial cells; Angpt-2 binds to and inhibits the Tie2 receptor, decreasing its phosphorylation as well as the downstream phosphorylation of Akt and FOXO1; this leads to FOXO1 activation and an increase expression of Angpt-2, generating a feedback loop. B. Model for the pathogenesis of angiodysplasia in VWD. In the absence of VWF, the increase in Angpt-2 disrupts vascular morphogenesis through multiple mechanisms: increased sprouting, impaired vascular remodelling and an imbalance between Angpt-1 and Angpt-2 in the gut. Figure generated with Biorender. C_FIG

cell biology↗

bioRxiv2020

The GPIbα intracellular tail - role in transducing VWF- and Collagen/GPVI-mediated signaling

Synergy between GPIb and GPVI signaling machineries has been suggested previously, however its molecular mechanism remains unclear. We generated a novel GPIb transgenic mouse (GPIb{Delta}sig/{Delta}sig) by CRISPR-Cas9 technology to delete the last 24 residues of the GPIb intracellular tail important for VWF-mediated signaling. GPIb{Delta}sig/{Delta}sig platelets bound VWF normally under flow but formed fewer filopodia on VWF/botrocetin, demonstrating that the deleted region does not affect ligand binding but appreciably impairs VWF-dependent signaling. Notably, while haemostasis was normal in GPIb{Delta}sig/{Delta}sig mice, GPIb{Delta}sig/{Delta}sig platelets exhibited defective responses after collagen-related-peptide stimulation and formed smaller aggregates on collagen-coated microchannels at low and high shears. Flow assays performed with plasma-free blood or in the presence of IIb{beta}3-or GPVI-blockers suggested reduced IIb{beta}3 activation contributes to the phenotype of the GPIb{Delta}sig/{Delta}sig platelets. Together, these results reveal a new role for the intracellular tail of GPIb in transducing both VWF-GPIb and collagen-GPVI signaling events in platelets. Summary statementGPIb and GPVI are two key receptors on the platelet surface. Using a novel transgenic mouse (GPIb{Delta}sig/{Delta}sig) that lacks the last 24 amino acids of the GPIb intracellular tail, we demonstrate the importance of this region not only in transducing signals in response to GPIb binding to VWF, but also for collagen-GPVI-mediated platelet responses revealing previously underappreciated receptor crosstalk between GPIb and GPVI.

cell biology↗

bioRxiv2018

Novel platelet-neutrophil interaction via activated αIIbβ3 mediates NETosis under flow

Platelet-neutrophil interactions are important for innate immunity, but also contribute to the pathogenesis of deep vein thrombosis, myocardial infarction and stroke. Here we report that, under flow, von Willebrand factor/glycoprotein Ib-dependent platelet priming induces integrin IIb{beta}3 activation that, in turn, mediates neutrophil and T-cell binding. Binding of platelet IIb{beta}3 to SLC44A2 on neutrophils leads to mechanosensitive-dependent production of highly prothrombotic neutrophil extracellular traps. A polymorphism in SLC44A2 (rs2288904-A) present in 22% of the population causes an R154Q substitution in an extracellular loop of SLC44A2 that is protective against venous thrombosis results in severely impaired binding to both activated IIb{beta}3 and VWF-primed platelets. This was confirmed using neutrophils homozygous for the SLC44A2 R154Q polymorphism. Taken together, these data reveal a previously unreported mode of platelet-neutrophil cross-talk, mechanosensitive NET production, and provide mechanistic insight into the protective effect of the SLC44A2 rs2288904-A polymorphism in venous thrombosis.\n\nSummaryPlatelets that are primed following interaction with von Willebrand factor under flow mediated direct interactions with neutrophils via activated platelet integrin, IIb{beta}3, and SLC44A2 on neutrophils. This interaction initiates signaling in a mechanosensitive manner that promotes neutrophil extracellular trap formation.

cell biology↗