Mechanochemistry of von Willebrand factor

AbstractVon Willebrand factor (VWF), a blood multimeric protein with a very high molecular weight, plays a crucial role in the primary haemostasis, the physiological process characterized by the adhesion of blood platelets to the injured vessel wall. Hydrodynamic forces are responsible for extensive conformational transitions in the VWF multimers that change their structure from a globular form to a stretched linear conformation. This feature makes this protein particularly prone to be investigated by mechanochemistry, the branch of the biophysical chemistry devoted to investigating the effects of shear forces on protein conformation. This review describes the structural elements of the VWF molecule involved in the biochemical response to shear forces. The stretched VWF conformation favors the interaction with the platelet GpIb and at the same time with ADAMTS-13, the zinc-protease that cleaves VWF in the A2 domain, limiting its prothrombotic capacity. The shear-induced conformational transitions favor also a process of self-aggregation, responsible for the formation of a spider-web like network, particularly efficient in the trapping process of flowing platelets. The investigation of the biophysical effects of shear forces on VWF conformation contributes to unraveling the molecular mechanisms of many types of thrombotic and haemorrhagic syndromes

The Von Willebrand factor-ADAMTS-13 axis: a two-faced Janus in bleeding and thrombosis

Von Willebrand factor (VWF), a blood multimeric protein with a very high molecular weight, plays a crucial role in the primary hemostasis, the physiological process characterized by the adhesion of blood platelets to the injured vessel wall. Hydrodynamic forces are responsible for the VWF multimers conformational transitions from a globular to a stretched linear conformation. These characteristics render this protein a valuable object to be investigated by mechanochemistry, the biophysical chemistry branch that studies the effects of shear forces on protein conformation. This review will focus on the structural elements of the VWF molecule involved in the biochemical response to shear forces. The stretched VWF conformation favors the interaction with the platelet GpIb and at the same time with ADAMTS-13, the zinc-protease that cleaves VWF in the A2 domain, limiting its prothrombotic capacity. It is important to consider the level or the function of VWF or ADAMTS-13 always in relation each other, keeping in mind that in many thrombotic forms of microangiopathies the reduction of the ratio between the ADAMTS-13 activity and the VWF level (lower than 0.5) can be a valuable parameter to predict a real thrombotic risk. Hence, a significant increase in VWF level alone, even without any reduction of ADAMTS-13 concentration, would still be responsible for a significant reduction of the ADAMTS-13/VWF ratio, which ultimately could reflect or predict a prothrombotic risk. Future studies will have to validate the concept whether ADAMTS-13/VWF ratio could a valuable and reliable biomarker to predict or confirm the presence of thrombotic risk in several morbid conditions

Effects of pegylated G-CSF on immune cell number and function in patients with gynecological malignancies

<p>Abstract</p> <p>Background</p> <p>Pegylated granulocyte colony-stimulating factor (G-CSF; pegfilgrastim) is a longer-acting form of G-CSF, whose effects on dendritic cell (DC) and regulatory T cell (Treg) mobilization, and on the <it>in vivo </it>and ex vivo release of immune modulating cytokines remain unexplored.</p> <p>Methods</p> <p>Twelve patients with gynecological cancers received carboplatin/paclitaxel chemotherapy and single-dose pegfilgrastim as prophylaxis of febrile neutropenia. Peripheral blood was collected prior to pegfilgrastim administration (day 0) and on days +7, +11 and +21, to quantify immunoregulatory cytokines and to assess type 1 DC (DC1), type 2 DC (DC2) and Treg cell mobilization. <it>In vitro</it>-differentiated, monocyte-derived DC were used to investigate endocytic activity, expression of DC maturation antigens and ability to activate allogeneic T-cell proliferation.</p> <p>Results</p> <p>Pegfilgrastim increased the frequency of circulating DC1 and DC2 precursors. In contrast, CD4⁺FoxP3⁺<it>bona fide </it>Treg cells were unchanged compared with baseline. Serum levels of hepatocyte growth factor and interleukin (IL)-12p40, but not transforming growth factor-β1 or immune suppressive kynurenines, significantly increased after pegfilgrastim administration. Interestingly, pegfilgrastim fostered <it>in vitro</it> monocytic<it/> secretion of IL-12p40 and IL-12p70 when compared with unconjugated G-CSF. Finally, DC populations differentiated <it>in vitro </it>after clinical provision of pegfilgrastim were phenotypically mature, possessed low endocytic activity, and incited a robust T-cell proliferative response.</p> <p>Conclusions</p> <p>Pegfilgrastim induced significant changes in immune cell number and function. The enhancement of monocytic IL-12 secretion portends favorable implications for pegfilgrastim administration to patients with cancer, a clinical context where the induction of immune deviation would be highly undesirable.</p

Do We Need to Define Therapeutic Ranges for Edoxaban Plasma Concentration?

Do We Need to Define Therapeutic Ranges for Edoxaban Plasma Concentration

Pathogenesis Of Portal Vein Thrombosis In Liver Cirrhosis: The Role of the ADAMTS13/VWF Unbalance

Increasing evidence shows a potential role of ADAMTS13 deficiency as a risk factor for the high prevalence of portal vein thrombosis (PVT) in cirrhotic patients. This deficiency, due to myofibroblastic transformation of hepatic stellate cells (HSCs), the source of ADAMTS13, is responsible for the prevalence of ultra large molecular weight multimers of von Willebrand factor (UL-VWF) in the hepatic microcirculation. This phenomenon would favor the prohaemostatic function of VWF, which, together with an elevation of coagulation FVIII, which is associated to VWF, could sustain microcirculatory thrombosis in the liver. These phenomena, triggering an increase of the intra-hepatic pressure, would cause a slowdown of the portal flow, favoring the occurrence of PVT. Although this scenario is justified by retrospective observational clinical studies, it will be mandatory to clarify the ADAMTS13 expression in HSCs associated with the activity of plasma ADAMTS13 in different stage of liver diseases. Hence, a prospective clinical trial (ClinicalTrials.gov Identifier: NCT03322696) is ongoing to unravel the linkage between all the actors involved in the complex phenomenon of PVT occurring in cirrhosi

Detection of Platelet-Activating Antibodies Associated with Vaccine-Induced Thrombotic Thrombocytopenia by Flow Cytometry: An Italian Experience

Rare cases of thrombocytopenia and thrombosis after anti-COVID-19 adenovirus-associated mRNA vaccines (VITT) due to platelet-activating anti-platelet-factor 4 (PF4)/polyanion antibod-ies have been reported. VITT laboratory diagnosis, similarly to heparin-induced thrombocytope-nia (HIT) diagnosis, requires immunoassays for anti-PF4/polyanion antibodies identification, such as ELISA assays and platelet-activating functional tests, such as heparin-induced platelet activation test (HIPA), to confirm their pathogenicity. We compared the flow cytometry (FC) measurement of platelet p-selectin exposure to the gold standard functional test HIPA for diagno-sis confirmation in 13 patients with a clinical VITT syndrome (6M/7F; median age 56 (33–78)) who resulted positive to anti-PF4/polyanion antibodies ELISA assays (12/13). FC and HIPA sim-ilarly identified three different patterns: (1) a typical non-heparin-dependent VITT pattern (seven and six patients by FC and HIPA, respectively); (2) low/no platelet activation in patients under IvIg therapy (five out of five and two out of four patients by FC and HIPA, respectively); (3) a HIT pattern. Antibodies investigated by FC became negative after 7, 17, and 24 days of therapy in three patients. FC measurement of P-selectin exposure was as sensitive as HIPA but simpler to de-tect anti-PF4/polyanion antibodies in VITT patients. FC could reliably discriminate VITT from HIT, thus helping for the choice of the anticoagulant

Laying the foundations for gene therapy in Italy for patients with haemophilia A: A Delphi consensus study

IntroductionCurrent treatment for haemophilia A involves factor VIII replacement or non-replacement (emicizumab) therapies, neither of which permanently normalise factor VIII levels. Gene therapy using adeno-associated viral (AAV) vectors is an emerging long-term treatment strategy for people with severe haemophilia A (PwSHA) that is likely to be available for clinical use in the near future. AimThis article proposes practical guidelines for the assessment, treatment, and follow-up of potential PwSHA candidates for AAV-based gene therapy. MethodUsing the Delphi method, a working group of Italian stakeholders with expertise in and knowledge of the care of adults with haemophilia A analysed literature for AAV-based gene therapy and drafted a list of statements that were circulated to a panel of Italian peers. During two rounds of voting, panel members voted on their agreement with each statement to reach a consensus. ResultsThe Delphi process yielded 40 statements regarding haemophilia A gene therapy, across five topics: (1) organisational model; (2) multidisciplinary team; (3) patient engagement; (4) laboratory surveillance; and (5) patient follow-up and gene therapy outcomes. The consensus was reached for all 40 statements, with the second round of voting needed for five statements. ConclusionUse of the hub-and-spoke organisational model and multidisciplinary teams are expected to optimise patient selection for gene therapy, as well as the management of dosing and patient follow-up, patient engagement, laboratory surveillance, and patient expectations regarding outcomes. This approach should allow the benefits of AAV-based gene therapy for haemophilia A to be maximised

ORal anticoagulants In fraGile patients with percutAneous endoscopic gastrostoMy and atrIal fibrillation: the (ORIGAMI) study

BACKGROUND: Randomized trials support the safety and efficacy of direct oral anticoagulants (DOACs) versus vitamin K antagonists (VKAs) in patients with nonvalvular atrial fibrillation, leading to increased use of these compounds. Crushed forms of DOACs have been shown to be reliable, but evidence supporting percutaneous endoscopic gastrostomy (PEG) delivery is lacking. PEG is a long-term option for enteral food and drug delivery in patients unable to maintain oral intake, bypassing the risks and disadvantages of parenteral nutrition.AIMS: The ORal anticoagulants In fraGile patients with percutAneous endoscopic gastrostoMy and atrIal fibrillation (ORIGAMI) study investigates the safety and efficacy of Edoxaban administered via PEG in patients with atrial fibrillation and a clinical indication for a long-term anticoagulation.DESIGN: In this prospective, single-centre observational study, 12 PEG-treated patients with indication to anticoagulation will receive edoxaban via PEG and will be followed up to 6 months. Plasma antifactor Xa activity and edoxaban concentrations will be assessed. Thromboembolic (ischaemic stroke, systemic embolism, venous thromboembolism) and bleeding events (Bleeding Academic Research Consortium and Thrombolysis in Myocardial Infarction) will be recorded at 1 and 6 months.PRELIMINARY CASES: A retrospective analysis of five atrial fibrillation cases undergoing PEG implantation at our Institution who received edoxaban via PEG showed plasma anti-FXa levels at a steady state of 146 ± 15 ng/ml, without major adverse event at a mean follow-up of 6 months.CONCLUSION: ORIGAMI prospectively investigates PEG-administration of edoxaban in PEG-treated patients requiring long-term anticoagulation. Our preliminary retrospective data support this route of DOAC administration. CLINICALTRIALS.GOV IDENTIFIER: NCT04271293

Frequency of left ventricular hypertrophy in non-valvular atrial fibrillation

Left ventricular hypertrophy (LVH) is significantly related to adverse clinical outcomes in patients at high risk of cardiovascular events. In patients with atrial fibrillation (AF), data on LVH, that is, prevalence and determinants, are inconsistent mainly because of different definitions and heterogeneity of study populations. We determined echocardiographic-based LVH prevalence and clinical factors independently associated with its development in a prospective cohort of patients with non-valvular (NV) AF. From the "Atrial Fibrillation Registry for Ankle-brachial Index Prevalence Assessment: Collaborative Italian Study" (ARAPACIS) population, 1,184 patients with NVAF (mean age 72 \ub1 11 years; 56% men) with complete data to define LVH were selected. ARAPACIS is a multicenter, observational, prospective, longitudinal on-going study designed to estimate prevalence of peripheral artery disease in patients with NVAF. We found a high prevalence of LVH (52%) in patients with NVAF. Compared to those without LVH, patients with AF with LVH were older and had a higher prevalence of hypertension, diabetes, and previous myocardial infarction (MI). A higher prevalence of ankle-brachial index 640.90 was seen in patients with LVH (22 vs 17%, p = 0.0392). Patients with LVH were at significantly higher thromboembolic risk, with CHA2DS2-VASc 652 seen in 93% of LVH and in 73% of patients without LVH (p &lt;0.05). Women with LVH had a higher prevalence of concentric hypertrophy than men (46% vs 29%, p = 0.0003). Logistic regression analysis demonstrated that female gender (odds ratio [OR] 2.80, p &lt;0.0001), age (OR 1.03 per year, p &lt;0.001), hypertension (OR 2.30, p &lt;0.001), diabetes (OR 1.62, p = 0.004), and previous MI (OR 1.96, p = 0.001) were independently associated with LVH. In conclusion, patients with NVAF have a high prevalence of LVH, which is related to female gender, older age, hypertension, and previous MI. These patients are at high thromboembolic risk and deserve a holistic approach to cardiovascular prevention