Prediction of Oscillations in Glycolysis in Ethanol-Consuming Erythrocyte-Bioreactors.

A mathematical model of energy metabolism in erythrocyte-bioreactors loaded with alcohol dehydrogenase and acetaldehyde dehydrogenase was constructed and analyzed. Such erythrocytes can convert ethanol to acetate using intracellular NAD and can therefore be used to treat alcohol intoxication. Analysis of the model revealed that the rate of ethanol consumption by the erythrocyte-bioreactors increases proportionally to the activity of incorporated ethanol-consuming enzymes until their activity reaches a specific threshold level.

Filterability of Erythrocytes in Patients with COVID-19.

For the first time, the influence of COVID-19 on blood microrheology was studied. For this, the method of filtering erythrocytes through filters with pores of 3.5 μm was used.

Ammonium removal by erythrocyte-bioreactors based on glutamate dehydrogenase from Proteus sp. jointly with porcine heart alanine aminotransferase.

Excessive ammonium blood concentration causes many serious neurological complications. The medications currently used are not very effective. To remove ammonium from the blood, erythrocyte-bioreactors containing enzymes that processing ammonium have been proposed.

Theoretical Analysis of the Built-in Metabolic Pathway Effect on the Metabolism of Erythrocyte-Bioreactors That Neutralize Ammonium.

The limitations of the efficiency of ammonium-neutralizing erythrocyte-bioreactors based on glutamate dehydrogenase and alanine aminotransferase reactions were analyzed using a mathematical model. At low pyruvate concentrations in the external medium (below about 0.3 mM), the main limiting factor is the rate of pyruvate influx into the erythrocyte from the outside, and at higher concentrations, it is the disappearance of a steady state in glycolysis if the rate of ammonium processing is higher than the critical value (about 12 mM/h).

Erythrocytes as Carriers: From Drug Delivery to Biosensors.

Drug delivery using natural biological carriers, especially erythrocytes, is a rapidly developing field. Such erythrocytes can act as carriers that prolong the drug's action due to its gradual release from the carrier; as bioreactors with encapsulated enzymes performing the necessary reactions, while remaining inaccessible to the immune system and plasma proteases; or as a tool for targeted drug delivery to target organs, primarily to cells of the reticuloendothelial system, liver and spleen. To date, erythrocytes have been studied as carriers for a wide range of drugs, such as enzymes, antibiotics, anti-inflammatory, antiviral drugs, etc.

Kaolin, used to trigger coagulation in thrombin generation test, increases sensitivity of the method in hemophilia patients.

: Thrombin generation test (TGT) is well established tool to research blood coagulation in plasma of hemophilia patients. Traditionally coagulation in this test is triggered by a tissue factor (TF), an extrinsic coagulation pathway activator. However, it is known that disorders of the intrinsic pathway are most important for coagulation in hemophilia.

Erythrocytes as bioreactors to decrease excess ammonium concentration in blood.

Increased blood ammonium concentrations cause neurological complications. Existing drugs are not always sufficiently effective. Alternatively, erythrocytes-bioreactors (EBRs) loaded with enzymes utilizing ammonium, were suggested for ammonium removal from blood.

Thrombodynamics, a new global coagulation test: Measurement of heparin efficiency.

The actual coagulation status may be reliably measured using only highly sensitive global functional tests; however, they are not numerous and all of them have disadvantages. Thrombodynamics (TD), a novel global coagulation test, is sensitive to hypo- and hypercoagulable states. The main properties of this test were investigated, and its capabilities for hemostasis analysis were verified through pharmacodynamic monitoring of the most widely used anticoagulants, heparins.

Rapid Elimination of Blood Alcohol Using Erythrocytes: Mathematical Modeling and In Vitro Study.

Erythrocytes (RBCs) loaded with alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALD) can metabolize plasma ethanol and acetaldehyde but with low efficiency. We investigated the rate-limiting factors in ethanol oxidation by these enzymes loaded into RBCs. Mathematical modeling and in vitro experiments on human RBCs loaded simultaneously with ADH and ALD (by hypoosmotic dialysis) were performed.

Moderate plasma dilution using artificial plasma expanders shifts the haemostatic balance to hypercoagulation.

Artificial plasma expanders (PEs) are widely used in modern transfusion medicine. PEs do not contain components of the coagulation system, so their infusion in large volumes causes haemodilution and affects haemostasis. However, the existing information on this effect is contradictory.

The modification of the thrombin generation test for the clinical assessment of dabigatran etexilate efficiency.

A new oral anticoagulant, dabigatran etexilate (DE, a prodrug of direct thrombin inhibitor (DTI) dabigatran), has been used clinically to prevent thrombosis. The assessment of dabigatran efficiency is necessary in some clinical cases, such as renal insufficiency, risk of bleeding, and drug interactions. However, a specific thrombin generation test (TGT) that is one of the most informative and sensitive to anticoagulant therapy (calibrated automated thrombinography (САТ)) shows a paradoxical increase of test parameters, such as endogenous thrombin potential (ETP) and peak thrombin, in patients receiving DE.

Application of Molecular Modeling to Development of New Factor Xa Inhibitors.

In consequence of the key role of factor Xa in the clotting cascade and absence of its activity in the processes that do not affect coagulation, this protein is an attractive target for development of new blood coagulation inhibitors. Factor Xa is more effective and convenient target for creation of anticoagulants than thrombin, inhibition of which may cause some side effects. This study is aimed at finding new inhibitors of factor Xa by molecular computer modeling including docking SOL and postdocking optimization DISCORE programs.

Thromboelastography, thrombin generation test and thrombodynamics reveal hypercoagulability in patients with multiple myeloma.

Patients with multiple myeloma (MM) are at increased risk of venous thromboembolism. Therefore, adequate laboratory control of hemostasis and subsequent adjustments of anticoagulant therapy are necessary. We studied hemostasis changes using thromboelastography (TEG), thrombin generation test (TGT) and thrombodynamics (TD) in primary MM patients (PMMpt, n=25) and patients in remission (RMMpt, n=34) during blood stem cell (BSC) mobilization.

Thrombin inhibitors based on single-stranded DNA aptamers.

Investigation of inhibitory effect of two single-stranded DNA thrombin-inhibiting aptamers (15TBA and 31TBA) on fibrin polymerization in fibrinogen solutions and comparison of anticoagulant properties of these aptamers by a new global coagulation test of thrombodynamics. Measurement of aptamers' functional stability in human plasma and blood in vitro in order to investigate the involvement of 3'-exonuclease in fast decrease of aptamers' functional activity in vivo. Thrombin inhibition activity was measured in a buffer system in vitro as effects of aptamers on fibrin polymerization.

Antiplatelet agents can promote two-peaked thrombin generation in platelet rich plasma: mechanism and possible applications.

Background: Thrombin generation assay is a convenient and widely used method for analysis of the blood coagulation system status. Thrombin generation curve (TGC) is usually bell-shaped with a single peak, but there are exceptions. In particular, TGC in platelet-rich plasma (PRP) can sometimes have two peaks.

Anticoagulant therapy: basic principles, classic approaches and recent developments.

The standard multipotent anticoagulants (unfractionated and low molecular weight heparins, antagonists of vitamin K) are commonly used for treatment and/or prophylaxis of different thrombotic complications, such as deep vein thrombosis, thrombophilia, pulmonary embolism, myocardial infarction, stroke and so on. Advantages and shortcomings of these anticoagulants are considered. The modern tendencies to use small selective direct inhibitors of thrombin or factor Xa are surveyed.

International seminar on the red blood cells as vehicles for drugs.

The first human transfusion was performed by the pioneer Dr Jean-Baptiste Denis in France in 1667 and now, three centuries later, around 50 millions blood units are transfused every year, saving millions of lives. Today, there is a new application for red blood cells (RBCs) in cellular therapy: the effective use of erythrocytes as vehicles for chemical or biological drugs. Using this approach, the therapeutic index of RBC-entrapped molecules can be significantly improved with increased efficacy and reduced side effects.

New synthetic thrombin inhibitors: molecular design and experimental verification.

Background: The development of new anticoagulants is an important goal for the improvement of thromboses treatments.

Objectives: The design, synthesis and experimental testing of new safe and effective small molecule direct thrombin inhibitors for intravenous administration.

Methods: Computer-aided molecular design of new thrombin inhibitors was performed using our original docking program SOL, which is based on the genetic algorithm of global energy minimization in the framework of a Merck Molecular Force Field.

A new drug form of blood coagulation factor IX: red blood cell-entrapped factor IX.

Background: Deficiency of factor IX causes hemophilia B, and primary treatment for hemophilia B is based on recurrent infusions of deficient factor IX. Frequent infusions of foreign protein diminish patients' quality of life, and increase the risk of development of immune reaction. We entrapped factor IX into erythrocytes-carriers (pharmacocytes) to prolong the drug's circulation life time, and to prevent immune response to the drug.

Mechanisms of action of recombinant activated factor VII in the context of tissue factor concentration and distribution.

Supraphysiological concentrations of recombinant activated factor VII (rVIIa, NovoSeven) are used to control bleeding in hemophilia. Current experimental evidence suggests that rVIIa may increase thrombin generation via two pathways: one being tissue factor (TF)-dependent and another being activated platelet-dependent. Contribution of TF to the rVIIa action may justify different administration profiles of rVIIa.

Platelet microparticle membranes have 50- to 100-fold higher specific procoagulant activity than activated platelets.

Platelet microparticles (PMPs) are small vesicles released from blood platelets upon activation. The procoagulant activity of PMPs has been previously mainly characterized by their ability to bind coagulation factors VIII and Va in reconstructed systems. It can be supposed that PMPs can contribute to the development of thrombotic complications in the pathologic states associated with the increase of their blood concentration.

Spatial propagation and localization of blood coagulation are regulated by intrinsic and protein C pathways, respectively.

Blood coagulation in vivo is a spatially nonuniform, multistage process: coagulation factors from plasma bind to tissue factor (TF)-expressing cells, become activated, dissociate, and diffuse into plasma to form enzymatic complexes on the membranes of activated platelets. We studied spatial regulation of coagulation using two approaches: 1), an in vitro experimental model of clot formation in a thin layer of plasma activated by a monolayer of TF-expressing cells; and 2), a computer simulation model. Clotting in factor VIII- and factor XI-deficient plasmas was initiated normally, but further clot elongation was impaired in factor VIII- and, at later stages, in factor XI-deficient plasma.