Increased Thrombus Formation Research Articles

Elevated plasma levels of factor VIII enhance arterial thrombus formation on erosive smooth muscle cell-rich neointima but not normal intima in rabbits

BackgroundPlaque erosion, a type of coronary atherothrombosis, involves superficial injury to smooth muscle cell (SMC)-rich plaques. Elevated levels of coagulation factor VIII (FVIII) correlate with an increased ischemic heart disease risk. FVIII may contribute to thrombus formation on eroded plaques. AimsWe aimed to elucidate the role of elevated FVIII in arterial thrombus formation within SMC-rich neointima in rabbits. Methods and resultsWe assessed the effect of recombinant human FVIII (rFVIII) on blood coagulation in vitro and platelet aggregation ex vivo. An SMC-rich neointima was induced through balloon injury to the unilateral femoral artery. Three weeks after the first balloon injury, superficial erosive injury and thrombus formation were initiated with a second balloon injury of the bilateral femoral arteries 45 min after the administration of rFVIII (100 IU/kg) or saline. The thrombus area and contents were histologically measured 15 min after the second balloon injury. rFVIII administration reduced the activated partial thromboplastin time and augmented botrocetin-induced, but not collagen- or adenosine 5′-diphosphate-induced, platelet aggregation. While rFVIII did not influence platelet-thrombus formation in normal intima, it increased thrombus formation on SMC-rich neointima post-superficial erosive injury. Enhanced immunopositivity for glycoprotein IIb/IIIa and fibrin was observed in rFVIII-administered SMC-rich neointima. Neutrophil count in the arterial thrombus on the SMC-rich neointima correlated positively with thrombus size in the control group, unlike the rFVIII group. ConclusionsIncreased FVIII contributes to thrombus propagation within erosive SMC-rich neointima, highlighting FVIII's potential role in plaque erosion-related atherothrombosis.

The use of percutaneous left atrial appendage occluder device in a patient with prior surgical ligation with incomplete exclusion: a case report

Abstract Background Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, and the most common cause of cardioembolic stroke. The left atrial appendage (LAA) is the main source of thrombus formation in patients with AF. Therapies include use of percutaneous LAA closure devices, or surgical LAA occlusion (LAAO). Despite these options, complete closure of the LAA is not always achieved, and residual communication between the LAA and atrium may result in increased thrombus formation. Although studies have analysed the use of percutaneous measures such as coils, plugs, or second occluder device deployment in LAA with peri-device leak (PDL), use of percutaneous occlude devices in surgically occluded LAA is far less studied. Case summary We present a case of a 79-year-old female patient who underwent LAAO device deployment within a surgically occluded LAA with PDL. She underwent 27 mm LAAO device (WATCHMANTM) deployment and all the P.A.S.S. (Position, Anchor, Size, and Seal) criteria were satisfied. Only 1.4 mm PDL was present. She was continued on apixaban and aspirin post-operatively. Post-operative transoesophageal echocardiogram at 6 weeks demonstrated trivial PDL measuring 1.49 mm. Patient was continued on aspirin and clopidogrel, with discontinuation of apixaban. Discussion Percutaneous LAAO device deployment in previously surgically ligated LAA with incomplete exclusion is a potential therapeutic option for patients with AF and a high bleeding risk seeking a minimally invasive strategy, in an attempt to de-escalate anticoagulation therapy.

Anti-PF4/Heparin Monoclonal Antibodies Induce Thrombus Formation in an Ex Vivo Endothelialized Microfluidic System

Introduction: Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin. Antibodies against platelet factor 4 (PF4) or a heparin/PF4 complex have been reported to activate platelets, neutrophils and possibly endothelial cells, resulting in thrombocytopenia, hypercoagulability and thromboembolic complications. While the impact of anti-PF4/heparin antibodies on platelet, neutrophil and monocyte activation has been extensively studied, the role of endothelial cells in HIT-associated thrombosis remains underexplored. In particular, the interactions between HIT-induced procoagulancy and endothelial cells under dynamic conditions is not completely analyzed. In this report, we investigated how HIT antibodies induce thrombosis in an endothelialized microfluidic system. Methods: Fibrinogen microfluidic channels were coated with confluent monolayer of human umbilical vein endothelial cells (HUVECs). Cells were primed with low-dose TNF-α to induce a sub-thrombotic endothelial activation, prior to perfusion of whole blood. Recalcified unstimulated or Thrombin Receptor Activator Peptide 6 (TRAP-6) activated whole blood was perfused at a venous flow rate. HIT-thrombosis model was established and tested with monoclonal anti-PF4/heparin antibodies in whole blood. In brief, whole blood was pre-incubated with unfractionated heparin (UFH, 0.2 IU/mL and 100 IU/mL). Next, anti-PF4/heparin antibodies were introduced to the whole blood mixture and incubated for 30 minutes. Whole blood was recalcified and perfused over resting or primed endothelial cells at a venous shear stress. Thrombus formation was recorded over time. Results: The endothelialized microfluidic model successfully captures sub-thrombotic conditions under venous shear. Activated platelets induced a procoagulant shift and three-dimensional thrombi. We applied our thrombosis model to investigate thrombus formation induced by a HIT mimicking monoclonal antibody. We show that the heparin-dependent platelet activation predicts the thrombotic response in the microfluidic system: HIT antibodies in absence of heparin did not exert a pro-thrombotic effect on activated endothelial cells. Co-incubation with 0.2 IU/mL UFH induced thrombosis, embolization of thrombus material and channel occlusion only when endothelial cells were primed with TNF-α. The pro-thrombotic effect of HIT antibodies was fully reversed at the super-therapeutic dose of 100 IU/mL UFH. Conclusions: HIT antibodies induce thrombosis and embolization in a system emulating physiological environment. For the first time, we present a comprehensive thrombosis model that incorporates the established thrombogenicity of HIT-mimicking antibodies. We show that our thrombosis model incorporates both endothelial- and blood-based control of thrombosis. Primed endothelial cells and antibody-induced procoagulancy trigger thrombosis in a concerted fashion, allowing investigation of the underlying mechanisms and possible preclinical evaluation of potential inhibitors of HIT-thrombosis. Figure 1, upper panel: Maximal thrombus surface area coverage of TNF-α primed endothelial cells, perfused with unstimulated, TRAP-6 activated or HIT-like IgG/heparin challenged whole blood. HIT-like IgG did not increase thrombus formation in absence of heparin. Addition of low-dose heparin exerted a strong pro-thrombotic effect, that was fully reversible with a super-therapeutic concentration of heparin. Lower panel: representative images of thrombi formed by HIT-like IgG in absence and under low or high-dose heparin. Platelets: green, Calcein-AM. Scale bar: 200 µm.

RATIONALE FOR PRESCRIBING ANTICOAGULANT THERAPY IN THE COMPLEX TREATMENT OF PURULENT-NECROTIC COMPLICATIONS OF DIABETIC FOOT SYNDROME

Abstract. This article is based on the study of hemostasis indicators in 25 patients with diabetic foot syndrome. Diabetic foot syndrome (DFS) develops against the background of diabetic neuropathy, micro- and macroaniopathy, osteoarthropathy, which lead to frequent traumatization of the soft tissues of the foot, infection with the subsequent development of purulent-necrotic processes on the foot, and in the course of progression leads to high limb amputations. According to the international federation, which deals with the problem of diabetes mellitus (DM), the 21st century is considered a pandemic of DM. It should be noted that the number of patients with diabetes is increasing every year. Patients with diabetes are characterized by an atherothrombotic state caused by multiple disorders in the hemostasis system. Hemostatic disorders in patients with diabetes are complex and include activation of natural mechanisms of the coagulation system, inhibition of fibrinolytic activity, and various platelet dysfunctions.
 The purpose of the study is to substantiate the appointment of anticoagulation therapy in patients with SDS.
 Materials and methods. On the basis of KNP KMKL No. 6 in Kyiv in 2023, for a period of 6 months, 69 patients with SDS were treated. The state of indicators of the coagulation link of the hemostasis system in 49 people was studied. At the same time, 26 patients had purulent-necrotic complications of the neuroischemic form of SDS, 23 people were healthy (comparison group). The patients were divided according to the article and age, according to the duration of diabetes mellitus, and according to the stages according to Wagner. The following indicators were determined for patients: prothrombin index (PTI), plasma recalcification time, fibrinogen, B-naphthol test, ethanol test, Willebrand factor, endothelin-1, coagulation factor (VIII), fibronectin.
 The results of the study and their discussion: Based on the study, 61.5 % of patients with SDS are of working age. Of them, 57.7 % are men, 42.3 % are women. The largest number of patients with SDS is observed in the group of patients who have had diabetes for more than 10 years - 57.7 %, and the largest number of patients with stage III-IV according to Wagner - 88.5 %. In patients with diabetes with neuroischemic form of SDS, the PTI level is increased by 28.8 % and the prothrombin time is shortened by 21 %, which indicates an increase in the activity of external blood clotting mechanisms. An increase in fibrinogen by 29.7 % indicates an increase in the activity of coagulation hemostasis. Willebrand factor increased by 34.5 %, coagulation factor (VIII) increased by 20.3 %, fibronectin increased by 83.01 %, which indicates an increase in aggregation and procoagulant processes, which in turn increases thrombus formation.
 Conclusion. Thus, with diabetic foot syndrome, hypercoagulation is observed, which leads to an increase in the level of thrombus formation, which justifies the appointment of anticoagulant therapy in the complex treatment of diabetic foot syndrome.

Endoplasmic reticulum protein 5 attenuates platelet endoplasmic reticulum stress and secretion in a mouse model.

Extracellular protein disulfide isomerases (PDIs), including PDI, endoplasmic reticulum protein 57 (ERp57), ERp72, ERp46, and ERp5, are required for invivo thrombus formation in mice. Platelets secrete PDIs upon activation, which regulate platelet aggregation. However, platelets secrete only ∼10% of their PDI content extracellularly. The intracellular role of PDIs in platelet function is unknown. Here, we aim to characterize the role of ERp5 (gene Pdia6) using platelet conditional knockout mice, platelet factor 4 (Pf4) Cre+/ERp5floxed (fl)/fl. Pf4Cre+/ERp5fl/fl mice developed mild macrothrombocytopenia. Platelets deficient in ERp5 showed marked dysregulation of their ER, indicated by a twofold upregulation of ER proteins, including PDI, ERp57, ERp72, ERp46, 78 kilodalton glucose-regulated protein (GRP78), and calreticulin. ERp5-deficient platelets showed an enhanced ER stress response to exvivo and invivo ER stress inducers, with enhanced phosphorylation of eukaryotic translation initiation factor 2A and inositol-requiring enzyme 1 (IRE1). ERp5 deficiency was associated with increased secretion of PDIs, an enhanced response to thromboxane A2 receptor activation, and increased thrombus formation invivo. Our results support that ERp5 acts as a negative regulator of ER stress responses in platelets and highlight the importance of a disulfide isomerase in platelet ER homeostasis. The results also indicate a previously unanticipated role of platelet ER stress in platelet secretion and thrombosis. This may have important implications for the therapeutic applications of ER stress inhibitors in thrombosis.

Supplemental fibrinogen restores thrombus formation in cardiopulmonary bypass-induced platelet dysfunction ex vivo

BackgroundMajor cardiac surgery related blood loss is associated with increased postoperative morbidity and mortality. Platelet dysfunction is believed to contribute to post-cardiopulmonary bypass (CPB)-induced microvascular bleeding. We hypothesised that moderately hypothermic CPB induces platelet dysfunction and that supplemental fibrinogen can restore in vitro thrombus formation. MethodsBlood from 18 patients, undergoing first-time elective isolated aortic valve surgery was drawn before CPB, 30 min after initiation of CPB, and after CPB and protamine administration, respectively. Platelet aggregation was quantified by optical aggregometry, platelet activation by flow-cytometric detection of platelet surface expression of P-selectin, annexin V, and activated glycoprotein IIb/IIIa, thrombus formation under flow and effect of supplemental fibrinogen (4 mg ml−1) on in vitro thrombogenesis. ResultsPost-CPB adenosine–diphosphate and TRAP-6-induced aggregation decreased by 40% and 10% of pre-CPB levels, respectively (P<0.0001). Although CPB did not change glycoprotein IIb/IIIa receptor expression, it increased the percentage of unstimulated P-selectin (1.2% vs 7%, P<0.01) positive cells and annexin V mean fluorescence intensity (15.5 vs 17.2, P<0.05), but decreased percentage of stimulated P-selectin (52% vs 26%, P<0.01) positive cells and annexin V mean fluorescence intensity (508 vs 325, P<0.05). Thrombus area decreased from 6820 before CPB to 5230 after CPB (P<0.05, arbitrary units [a.u.]). Supplemental fibrinogen increased thrombus formation to 20 324 and 11 367 a.u. before CPB and after CPB, respectively (P<0.001), thereby restoring post-CPB thrombus area to levels comparable with or higher than pre-CPB baseline. ConclusionsSingle valve surgery using moderately hypothermic CPB induces partial platelet dysfunction. Thrombus formation was restored in an experimental study design by ex vivo supplementation of fibrinogen.

The SARS-CoV-2 responsible for phlegmasia cerulea dolens: a case report

The authors report the case of a COVID-19 patient who presented with phlegmasia cerulea dolens (PCD) of the left lower limb, so he benefited from aponeurotomies of the internal and anterolateral muscular compartments. The severe acute respiratory syndrome coronavirus 2 involves an inflammatory process in thrombotic events in COVID-19 patients, including a cytokine storm. PCD evolves in three semiological phases: venous stasis, weakening of the pulses, and the constitution of major ischemia. In the literature, the authors find many reports that have been published regarding increased thrombus formation in COVID-19 patients; these include DVT formation, pulmonary embolism, and stroke. Nevertheless, publications concerning PCD in COVID-19 patients remain rare. Although the severe acute respiratory syndrome coronavirus 2 remains a thrombogenic pathology, systematic anticoagulation is the subject of hypothesis. Hence the importance of regular monitoring of markers of vascular thrombosis.

Platelet Phosphatidylserine Is the Critical Mediator of Increased Thrombus Formation in Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a severe adverse event that is caused by the interaction of platelets with ultra-large platelet factor 4 (PF4)/heparin IgG-immune complexes. Previous studies have shown that HIT Abs harbour the potential to interact with PLT Fc-gamma-RIIA leading to PLT activation and interplay with different actors of the innate and adaptive immune system. Despite this mechanistic insights, the role of different HIT Ab-induced PLT subpopulations that might contribute to an increased pro-thrombotic potential and severe patient outcome, remains poorly understood. In this study, we hypothesized that PF4/heparin HIT Abs induce a procoagulant PLT response that contribute to an increased pro-thrombotic environment. Using flow cytometry, we found that HIT patient Abs have the capability to induce a procoagulant (P-Selectin/phosphatidylserine double positive) PLT phenotype (p=0.0039) with increased thrombin generation potential (p<0.0001). Most importantly, the perfusion of whole blood samples that were spiked with HIT Ab-induced procoagulant PLTs resulted in significant increase of procoagulant (Annexin-V positive) PLT and fibrin deposition. Interestingly, Fc-gamma-RIIA inhibition via monoclonal antibody IV.3 resulted in a nearly complete abrogation of HIT Ab-induced thrombus formation, indicating that PLT Fc-gamma-RIIA signalling mechanisms are pivotal for Ab-induced pro-thrombotic PLT potential (p=0.0108, Figure 1A). Moreover, also the prostacyclin analogue Iloprost prevented procoagulant PLTs and increased thrombus formation despite the presence of HIT Abs and low dose (0.2 IUs/mL) heparin (p=0.0029). A finding that might be most probably due to increased intracellular concentrations of the second messenger cAMP due to increased PKA activity. To deeper investigate how increased CD62p expression and high PS externalization on the procoagulant PLT surface contribute to the prothrombotic potential of HIT Ab-induced procoagulant PLTs, we performed specific inhibition experiments. Although a marked reduction of neutrophil granulocyte deposition was observed, blocking of PLT CD62p did not reduced HIT Ab-induced increased thrombin generation or thrombus formation. In contrast, procoagulant PLTs that were treated with lactadherin, a PS binding and blocking protein resulted in a significant reduction of thrombin generation (p=0.0040) and thrombus formation compared to the vehicle control (p=0.0005, Figure 1B). Findings of our study indicate that HIT patient Abs harbour the ability to induce procoagulant PLTs via PLT FcγRIIA mediated signalling pathways. The observation that Iloprost reduced the formation of procoagulant PLTs and most importantly inhibits thrombus formation indicates a potential therapeutic use. Most importantly, based on our mechanistic studies we conclude that increased PS on the surface of procoagulant PLTs might be the causing factor for increased pro-thrombotic potential observed in HIT. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

One night of sleep deprivation induces release of small extracellular vesicles into circulation and promotes platelet activation by small EVs.

Extracellular vesicles (EVs) are emerging as key players in intercellular communication. Few studies have focused on EV levels in subjects with sleep disorders. Here, we aimed to explore the role of acute sleep deprivation on the quantity and functionality of circulating EVs, and their tissue distribution. EVs were isolated by ultracentrifugation from the plasma of volunteers and animals undergoing one night of sleep deprivation. Arterio‐venous shunt, FeCl3 thrombus test and thrombin‐induced platelet aggregation assay were conducted to evaluate the in vivo and in vitro bioactivity of small EVs. Western blotting was performed to measure the expression of EV proteins. The fate and distribution of circulating small EVs were determined by intravital imaging. We found that one night of sleep deprivation triggers release of small EVs into the circulation in both healthy individuals and animals. Injection of sleep deprivation‐liberated small EVs into animals increased thrombus formation and weight in thrombosis models. Also, sleep deprivation‐liberated small EVs promoted platelet aggregation induced by thrombin. Mechanistically, sleep deprivation increased the levels of HMGB1 protein in small EVs, which play important roles in platelet activation. Furthermore, we found sleep deprivation‐liberated small EVs are more readily localize in the liver. These data suggested that one night of sleep deprivation is a stress for small EV release, and small EVs released here may increase the risk of thrombosis. Further, small EVs may be implicated in long distance signalling during sleep deprivation‐mediated adaptation processes.

Externalization of Mitochondrial PDCE2 on Irradiated Endothelium as a Target for Radiation-Guided Drug Delivery and Precision Thrombosis of Pathological Vasculature.

Endothelial cells are highly sensitive to ionizing radiation, and exposure leads to multiple adaptive changes. Remarkably, part of this response is the translocation of normally intracellular proteins to the cell surface. It is unclear whether this ectopic expression has a protective or deleterious function, but, regardless, these surface-exposed proteins may provide unique discriminatory targets for radiation-guided drug delivery to vascular malformations or tumor vasculature. We investigated the ability of an antibody–thrombin conjugate targeting mitochondrial PDCE2 (E2 subunit of pyruvate dehydrogenase) to induce precision thrombosis on irradiated endothelial cells in a parallel-plate flow system. Click-chemistry was used to create antibody–thrombin conjugates targeting PDCE2 as the vascular targeting agent (VTA). VTAs were injected into the parallel-plate flow system with whole human blood circulating over irradiated cells. The efficacy and specificity of fibrin-thrombus formation was assessed relative to non-irradiated controls. The PDCE2-targeting VTA dose-dependently increased thrombus formation: minimal thrombosis was induced in response to 5 Gy radiation; doses of 15 and 25 Gy induced significant thrombosis with equivalent efficacy. Negligible VTA binding or thrombosis was demonstrated in the absence of radiation or with non-targeted thrombin. PDCE2 represents a unique discriminatory target for radiation-guided drug delivery and precision thrombosis in pathological vasculature.

Iron deficiency anemia and thrombosis risk in children-revisiting an old hypothesis.

Iron deficiency anemia has a high prevalence in children and has repeatedly been implicated as a risk factor for arterial and venous thrombosis. As an effective therapy for iron deficiency anemia is available, understanding the association between this form of anemia and the potentially severe thrombosis phenotype is of major clinical interest. Recent findings shed light on pathophysiology of hypercoagulability resulting from iron-restricted erythropoiesis. Specifically, an animal model of induced iron deficiency allowed identifying multiple mechanisms, by which iron deficiency anemia results in increased thrombus formation and thrombus progression both in arterial and venous thrombosis. These findings complement and support conclusions derived from clinical data. The purpose of this mini review is to summarize current evidence on the association of iron deficiency anemia and thrombosis. We want to increase the awareness of iron deficiency as a risk factor for thrombosis in the pediatric population. We discuss how novel pathophysiological concepts can be translated into the clinical settings and suggest clinical studies on prevention and treatment strategies in high-risk patient groups.

ПОСТЛУЧЕВЫЕ ИЗМЕНЕНИЯ СОДЕРЖАНИЯ В КРОВИ ТРОМБОЦИТОВ И ИХ ФУНКЦИОНАЛЬНОЙ АКТИВНОСТИ

The action of ionizing radiation on the body leads to the development of various pathological disorders in organs and tissues. In the first place are pathologies of the cardiovascular system. They are preceded by disorders in the blood system. There are general patterns in changes in the qualitative and quantitative composition of peripheral blood under the influence of ionizing radiation. Among cellular elements, platelets and their interaction with vascular endothelial cells play a leading role in changing the hemodynamic properties of blood. The angiotrophic function of platelets may be impaired due to changes in their number and/or functional activity. After irradiation at a dose of 1 Gy, phase changes in the number of platelets were observed in the blood of rats during the rehabilitation period. On the 3rd day of the post-radiation period, the concentration of platelets and the value of thrombocrit corresponded to those of the control group. On the 10th day, the number of platelets and the value of thrombocrit decreased in irradiated rats. In the long term after irradiation (30s and 90s), these indicators were restored to normal values. The distribution width of platelets and their average volume did not change during all the studied periods of the post-radiation period. After irradiation at a dose of 1 Gy, changes in the aggregation ability of platelets were noted when the aggregation inducer ADP was introduced at a low concentration (2.4 ± 10-6M). On the 3rd and 30th days, the irradiated sample was divided into two groups: individuals with a degree of platelet reactivity corresponding to the control, and with high reactivity. On the 10th day, among the platelets of irradiated individuals, a tendency to shift the indicators of the degree and rate of aggregation towards reduced aggregation activity prevails. In the long term (90th day) of the post-radiation period, the irradiated animals showed a prolongation of the period of change in the shape of platelets and a weakening of the reaction to aggregation inducers, which contributes to hemorrhagic manifestations. Thus, the data obtained indicate that in the short term after irradiation, the tendency to increased thrombus formation and the development of ischemic damage prevails, and in the long term (day 90), aggregation activity decreases and the risk of bleeding increases.

Risks of thrombosis: genotype and phenotype of blood coagulation factor V

The review is devoted to the key component of plasma hemostasis — blood coagulation factor V. The structure of this protein and the F5 gene encoding it, its role in the hemostasis system, interaction with other coagulation factors and the natural anticulant protein C are considered. Particular attention is paid to the genetic defects of F5, which determine both hemorrhagic complications and a hereditary tendency to increased thrombus formation. Among the latter, the Leiden mutation of coagulation factor V (FV Leiden), which is hereditary thrombophilia and is considered as a risk factor for the development of venous thromboembolic complications, is described in detail.

Comparing Velocity and Mean Arterial Pressure to Assess Pulsatility in Patients with Continuous Flow Left Ventricular Assist Devices

<h3>Purpose</h3> An increasing number of end-stage heart failure patients are supported by continuous-flow Left Ventricular Assist Devices (cfLVADs). In these patients, accurate assessment of arterial pulsatility remains a challenge because of diminished pulse pressure. Limited pulsatility in modern cfLVADs itself can be associated with adverse events such as stroke. Our study investigates the value of simultaneous arterial pressure and arterial blood velocity assessment in cfLVAD patients. <h3>Methods</h3> Both velocity (cm/s) and pressure (mmHg) data were collected during routine follow up. Pressure was measured using a brachial cuff oscillometry system (Sphygmocor XCel) providing a systolic and diastolic readings, while velocity was measured using a digital doppler (Huntleigh) from the brachial artery. Velocity measurements obtained included peak, minimum, average velocity and pulsatility index. Pressure measurements obtained were systolic and diastolic which allowed us to derive a mean arterial pressure (MAP) from the brachial artery. <h3>Results</h3> From a total of 24 patients (88% males), there were 44 velocity and pressure measurements. Mean device support duration was 240 days (SD 116). Mean derived brachial MAP was 85 mmHg (SD 9), whereas mean peak brachial artery velocity was 14 cm/s (SD 9). Mean pulsatility index was 2 (SD 2). Correlation analysis using Spearman's rho demonstrated a significant inverse relationship between Brachial derived MAP and Peak velocity (Rho=-0.41, p=0.007). <h3>Conclusion</h3> Arterial doppler measurements may provide incremental value over purely pressure-based measurements. The inverse relationship between derived MAP and peak velocity in this study may be partially explained by the degree of arterial compliance. In turn, this provides significant information on the relationship between higher MAP and lower blood velocity to subsequently explain increased thrombus formation and stroke rate due to longer transit time of blood.

COVID-19-associated orthostatic hypotension syndrome: direct and indirect mechanisms of development

Background. The article presents an observation of the clinical case of orthostatic hypotension that developed after an infection caused by the SARS-CoV-2 virus. The issues of etiology, pathogenesis, diagnosis are outlined. The complexity of diagnosis at the stage of clinical observation is due to the comorbidity of possible mechanisms and the difficulty of determining the primary factor. Taking into account the study of variants of direct and indirect action of this 2019-nCoV, the description of the clinical observation of orthostatic hypotension supplements the data on the spectrum of manifestations of this disease.&#x0D; Aim. Analysis of the clinical case of the development of orthostatic hypotension in the post-acute period of COVID-19.&#x0D; Material. When conducting a literature review on the selected topic, various sources were considered. The search depth was over 7 years. For the recruitment of literature, Internet platforms UpToDate, PubMed, Medscape were used. Russian and foreign sources were studied.&#x0D; Methods. Anamnesis collection, objective research, specialized tests, laboratory and instrumental research methods, study of disease history, literature sources on orthostatic hypotension and the effect of COVID-19 on the autonomic nervous system.&#x0D; Results. The analysis of this case with the determination of the leading mechanism of orthostatic hypotension is extremely difficult. Probably, there is a combination of factors: direct and indirect effects on the nervous system at COVID-19. The direct effect is associated with the interaction of the virus with the angiotensin converting enzyme 2 receptors in the nervous system, which causes a significant increase in the concentration of bradykinin and the development of hypotension. An indirect effect is due to both increased thrombus formation with the development of PE, and autonomic dysfunction, within the framework of secondary polyneuropathy of fine fibers.&#x0D; Conclusion. It is likely that in the near future the number of such patients in the practice of doctors will increase, therefore, timely and correct diagnosis of these conditions, with their careful management, will be the fundamental postulates in the recovery of patients. Drawing attention to this topic will possibly expand our understanding of the spectrum of complications of COVID-19 and will greatly complement the information available today.

Upregulation of cAMP prevents antibody-mediated thrombus formation in COVID-19

AbstractThromboembolic events are frequently reported in patients infected with the SARS-CoV-2 virus. The exact mechanisms of COVID-19-associated hypercoagulopathy, however, remain elusive. Recently, we observed that platelets (PLTs) from patients with severe COVID-19 infection express high levels of procoagulant markers, which were found to be associated with increased risk for thrombosis. In the current study, we investigated the time course as well as the mechanisms leading to procoagulant PLTs in COVID-19. Our study demonstrates the presence of PLT-reactive IgG antibodies that induce marked changes in PLTs in terms of increased inner-mitochondrial transmembrane potential (Δψ) depolarization, phosphatidylserine (PS) externalization, and P-selectin expression. The IgG-induced procoagulant PLTs and increased thrombus formation were mediated by ligation of PLT Fc-γ RIIA (FcγRIIA). In addition, contents of calcium and cyclic-adenosine-monophosphate (cAMP) in PLTs were identified to play a central role in antibody-induced procoagulant PLT formation. Most importantly, antibody-induced procoagulant events, as well as increased thrombus formation in severe COVID-19, were inhibited by Iloprost, a clinically approved therapeutic agent that increases the intracellular cAMP levels in PLTs. Our data indicate that upregulation of cAMP could be a potential therapeutic target to prevent antibody-mediated coagulopathy in COVID-19 disease.

Coronavirus disease 2019 (COVID-19): NETosis-associated mechanisms of progression and prospects for therapy regulating the formation of neutrophil extracellular traps (NETs)

Infectious disease COVID-19 caused by the SARS-CoV-2 coronavirus is characterized by high contagiousness, complexity of pathogenesis and unpredictability of the clinical course. In severe cases, which are especially susceptible to men, the elderly and people with underlying medical conditions such as obesity, diabetes, hypertension, cardiovascular and chronic respiratory diseases, the infection leads to respiratory failure and death due to the development of an extensive inflammatory reaction. As a result of many studies, it has been established that one of the leading causes of the severe course and death of patients with COVID-19 is the development of coagulopathy, that is, increased thrombus formation in small vessels due to excessive activity of neutrophils, which form the so-called neutrophil extracellular traps (NETs). Although NETs play a useful role in protecting their host from pathogens, their overgrowth can trigger a cascade of adverse reactions including: the production of antibodies against the host’s DNA (autoimmunization); damage to surrounding tissue; or the occurrence of thromboembolic complications. Therefore, extracellular neutrophil traps and their markers have been identified as targets for new therapeutic strategies aimed at reducing the severity of COVID-19 disease and/or mortality. This article describes the structure of NETs, as well as analyzes the molecular mechanisms that contribute to their overgeneration. In addition, the prospects for COVID-19 therapy aimed at regulating the formation of extracellular traps by creating drugs both limiting the production of NET structures and dissolving their excess amounts in the body of patients are discussed.

Titanium dioxide nanoparticles enhance thrombosis through triggering the phosphatidylserine exposure and procoagulant activation of red blood cells

BackgroundExpanding biomedical application of anatase titanium dioxide (TiO2) nanoparticles (NPs) is raising the public concern on its potential health hazards. Here, we demonstrated that TiO2 NPs can increase phosphatidylserine (PS) exposure and procoagulant activity of red blood cells (RBCs), which may contribute to thrombosis.ResultsWe conducted in vitro studies using RBCs freshly isolated from healthy male volunteers. TiO2 NPs exposure (≦ 25 μg/mL) induced PS exposure and microvesicles (MV) generation accompanied by morphological changes of RBCs. While ROS generation was not observed following the exposure to TiO2 NPs, intracellular calcium increased and caspase-3 was activated, which up-regulated scramblase activity, leading to PS exposure. RBCs exposed to TiO2 NPs could increase procoagulant activity as measured by accelerated thrombin generation, and enhancement of RBC-endothelial cells adhesion and RBC-RBC aggregation. Confirming the procoagulant activation of RBC in vitro, exposure to TiO2 NPs (2 mg/kg intravenously injection) in rats increased thrombus formation in the venous thrombosis model.ConclusionCollectively, these results suggest that anatase TiO2 NPs may harbor prothrombotic risks by promoting the procoagulant activity of RBCs, which needs attention for its biomedical application.

СORONAVIRUS INFECTION WITH AN OBESITY

Summary. Relevance of the topic: most of the world is obese and there are enough cases of the impact of this pathology on the development of a complicated and severe course of novel coronavirus (COVID-19) infection. Purpose of the study: to study literature data on the effect of obesity on the course of novel coronavirus infection. Objectives : 1. To consider obesity as a factor contributing to the intensification of inflammatory reactions. 2. To study the etiology and pathogenesis of COVID-19 infection. 3. To establish the relationship between obesity and complications arising from coronavirus infection. Results. The most common feature of COVID-19 is severe acute respiratory syndrome caused by progressive lung consolidation. There is a positive correlation between the duration of COVID-19 infection and the degree of interstitial fibrosis. Extensive pulmonary fibrosis is one of the main causes of pulmonary consolidation due to the excessive extracellular matrix component produced by activated myofibroblasts [7]. Pulmonary lipofibroblasts are a special type of adipocytes that contain typical lipid droplets and are close to the second type of alveolar epithelial cells of the pulmonary interstitium. Lipofibroblasts may result from ectopic fat deposition, which plays a vital role in the progression of COVID-19 in these patients. When exposed to various stimulants, such as hyperoxia and infection of lung lipofibroblasts, a transdifferentiated myogenic phenotype called myofibroblasts occurs, which causes pulmonary fibrosis [10]. A significant number of obese patients have impaired glucose metabolism, which is considered a risk factor and leads to death. SARS infection has been found to cause hyperglycemia in some patients due to dysfunction of the islets of the pancreas as a result of a viral attack. A similar effect occurs after infection with SARS-COV-2. This explains why 52% of those infected with SARS-COV-2 had hyperglycemia. The level of glucose increase in metabolic disorders in obese patients can be much higher. Hyperglycemia leads to a number of complications, including osmotic imbalance of fluid and electrolytes, hyperosmolar non-ketonemic coma, worsening skeletal muscle catabolism, impaired wound healing, altered coagulation, and increased susceptibility to infections [4]. In addition, hyperglycemia impairs the body's immune function. All of this worsens the clinical outcome of COVID-19. Notably, proper blood glucose control reduces mortality in critically ill patients, highlighting the importance of blood glucose control. Conclusion. The relationship between obesity as a factor complicating the course of SARS-COV-2 infection has been shown. This mainly concerns the development of a cytokine storm due to the release of IL-1, IL-6, IL-10 by adipose tissue, as well as TNF- α . It should be noted that obesity affects the occurrence of concomitant metabolic diseases in patients, such as type 2 diabetes mellitus, coronary heart disease, atherosclerosis, etc., leading to acute myocardial infarction, increased thrombus formation and many other serious conditions. In addition, it is difficult for obese patients to provide specialized medical care when connecting to a ventilator, preventing pressure ulcers and attaching a secondary infection.

СORONAVIRUS INFECTION WITH AN OBESITY

Summary. Relevance of the topic: most of the world is obese and there are enough cases of the impact of this pathology on the development of a complicated and severe course of novel coronavirus (COVID-19) infection. Purpose of the study: to study literature data on the effect of obesity on the course of novel coronavirus infection. Objectives : 1. To consider obesity as a factor contributing to the intensification of inflammatory reactions. 2. To study the etiology and pathogenesis of COVID-19 infection. 3. To establish the relationship between obesity and complications arising from coronavirus infection. Results. The most common feature of COVID-19 is severe acute respiratory syndrome caused by progressive lung consolidation. There is a positive correlation between the duration of COVID-19 infection and the degree of interstitial fibrosis. Extensive pulmonary fibrosis is one of the main causes of pulmonary consolidation due to the excessive extracellular matrix component produced by activated myofibroblasts [7]. Pulmonary lipofibroblasts are a special type of adipocytes that contain typical lipid droplets and are close to the second type of alveolar epithelial cells of the pulmonary interstitium. Lipofibroblasts may result from ectopic fat deposition, which plays a vital role in the progression of COVID-19 in these patients. When exposed to various stimulants, such as hyperoxia and infection of lung lipofibroblasts, a transdifferentiated myogenic phenotype called myofibroblasts occurs, which causes pulmonary fibrosis [10]. A significant number of obese patients have impaired glucose metabolism, which is considered a risk factor and leads to death. SARS infection has been found to cause hyperglycemia in some patients due to dysfunction of the islets of the pancreas as a result of a viral attack. A similar effect occurs after infection with SARS-COV-2. This explains why 52% of those infected with SARS-COV-2 had hyperglycemia. The level of glucose increase in metabolic disorders in obese patients can be much higher. Hyperglycemia leads to a number of complications, including osmotic imbalance of fluid and electrolytes, hyperosmolar non-ketonemic coma, worsening skeletal muscle catabolism, impaired wound healing, altered coagulation, and increased susceptibility to infections [4]. In addition, hyperglycemia impairs the body's immune function. All of this worsens the clinical outcome of COVID-19. Notably, proper blood glucose control reduces mortality in critically ill patients, highlighting the importance of blood glucose control. Conclusion. The relationship between obesity as a factor complicating the course of SARS-COV-2 infection has been shown. This mainly concerns the development of a cytokine storm due to the release of IL-1, IL-6, IL-10 by adipose tissue, as well as TNF- α . It should be noted that obesity affects the occurrence of concomitant metabolic diseases in patients, such as type 2 diabetes mellitus, coronary heart disease, atherosclerosis, etc., leading to acute myocardial infarction, increased thrombus formation and many other serious conditions. In addition, it is difficult for obese patients to provide specialized medical care when connecting to a ventilator, preventing pressure ulcers and attaching a secondary infection.