Hypochlorite-induced oxidation of fibrinogen: Effects on its thermal denaturation and fibrin structure.

BACKGROUND: Human fibrinogen, which plays a key role in plasma haemostasis, is a highly vulnerable target for oxidants. Fibrinogen undergoes posttranslational modifications that can potentially disrupt protein structure and function. METHODS: For the first time, by differential scanning calorimetry, dynamic and elastic light scattering and confocal laser scanning microscopy, the consequences of HOCl/-OCl-induced oxidation of fibrinogen on its thermal denaturation, molecular size distribution and fibrin clot network have been explored. RESULTS: Within a wide range of HOCl/-OCl concentrations (50-300 µM), the molecular size distribution remained unimodal; however, the average size of the hydrated molecules decreased. HOCl/-OCl-induced oxidation of fibrinogen resulted in the diminished thermal stability of regions D and E. As evidenced by elastic light scattering and confocal laser scanning microscopy, HOCl/-OCl caused the formation of abnormal fibrin with a decreased diameter of individual fibres. CONCLUSIONS: The current results along with data from previous studies enable one to conclude that the effect of HOCl/-OCl-mediated oxidation on the thermal stability of region D is influenced directly by oxidative damage to the D region structure. Since the E region is not subjected to oxidative modification, its structural damage is likely to be mediated by the oxidation of other protein structures, in particular α-helical coiled-coils. GENERAL SIGNIFICANCE: The experimental findings acquired in the current study could help to elucidate the consequences of oxidative stress in vivo on damage to the structure of fibrinogen/fibrin under the action of different ROS species.

Anticoagulants for Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is a multifactorial syndrome with a plethora of progressive, degenerative changes in the brain parenchyma, but also in the cerebrovascular and hemostatic system. A therapeutic approach for AD is reviewed, which is focused on the role of amyloid-ß protein (Aß) and fibrin in triggering intra-brain vascular dysfunction and connected, cognitive decline. It is proposed that direct oral anticoagulants (DOACs) counteract Aß-induced pathological alterations in cerebral blood vessels early in AD, a condition, known as cerebral amyloid angiopathy (CAA). By inhibiting thrombin for fibrin formation, anticoagulants can prevent accumulations of proinflammatory thrombin and fibrin, and deposition of degradation-resistant, Aß-containing fibrin clots. These fibrin-Aß clots are found in brain parenchyma between neuron cells, and in and around cerebral blood vessels in areas of CAA, leading to decreased cerebral blood flow. Consequently, anticoagulant treatment could reduce hypoperfusion and restricted supply of brain tissue with oxygen and nutrients. Concomitantly, hypoperfusion-enhanced neurodegenerative processes, such as progressive Aß accumulation via synthesis and reduced perivascular clearance, neuroinflammation, and synapse and neuron cell loss, could be mitigated. Given full cerebral perfusion and reduced Aß- and fibrin-accumulating and inflammatory milieu, anticoagulants could be able to decrease vascular-driven progression in neurodegenerative and cognitive changes, present in AD, when treated early, therapeutically, or prophylactically.

Cancer stromal targeting therapy to overcome the pitfall of EPR effect.

Many animal experiments performed worldwide have proven EPR effects However, it is hard to say that the EPR effect works in clinical practice. In the case of hematological malignancies, the administered anticancer agents (ACA) can physically interact with the malignant cells, making it easier to reflect in vitro data. In solid tumors, however, the extravasated ACAs must diffuse evenly within the whole tumor mass. Therefore, the cancer stroma and the tumor mass itself can be obstacles to drug delivery systems (DDS) including antibody therapeutics. We have demonstrated that hypercoagulability caused by cancer forms cancer stroma. We further showed that the more aggressive the cancer, the greater the deposition of insoluble fibrin (IF) in cancer tissue. In this background, we decided to create monoclonal antibody (mAb) that specifically binds to IF. After a long effort, a new and unique IF-specific mAb was developed. Subsequently, anti-IF mAb conjugated with an ACA using a V-L-K linker which can be cut by plasmin. Because plasmin is activated only during IF formation, the ACA is released from the ADC only when the conjugate is bound to the IF. The released ACA may readily get to cancer cells through the stromal obstacle because of its small size. The ACA also damages the capillary that nourish cancer cells. We have named this strategy cancer (CA) stroma (S) targeting (T) therapy, or CAST therapy.

Produção e purificação integrada de protease fibrinolítica de Mucor subtilissimus UCP 1262 / Integrated production and purification of fibrinolytic protease from Mucor subtilissimus UCP 1262

As enzimas fibrinolíticas podem ser obtidas de micro-organismos por meio de processos fermentativos. O presente trabalho teve como objetivo avaliar a produção e extração integrada da protease fibrinolítica de Mucor subtilissimus UCP 1262 usando sistema de duas fases aquosas (SDFA). O processo integrado foi realizado para avaliar a produção, partição e recuperação da protease fibrinolítica, segundo planejamento experimental 23, utilizando como variáveis independentes a massa molar do polietileno glicol (PEG), a concentração do PEG e a concentração do sulfato de sódio. A maior atividade fibrinolítica (15,40U/mL) foi obtida na fase rica em sulfato de sódio no ensaio composto por 10% de sal e 18% de PEG 8000 (g/mol). Recuperações superiores a 80% foram obtidas. A protease fibrinolítica apresentou pH ótimo 7,0, estabilidade entre os pH 6,0 e 8,5, temperatura ótima 50°C, sendo estável de 10°C a 50°C. A enzima foi classificada como uma serino protease, com massa molecular de 52kDa. Como resultado, o processo é notavelmente eficaz para pré-purificar a protease fibrinolítica com baixo custo e rapidez significativa. Quando comparada a outras técnicas de produção e purificação isoladas, a fermentação extrativa é um processo digno a ser substituto das etapas iniciais de separação convencionais.(AU)

Fibrinolytic enzymes can be obtained from microorganisms through fermentative processes. The study aimed to evaluate the fibrinolytic protease production and integrated extraction from Mucor subtilissimus UCP 1262 by extractive fermentation using Aqueous Two-Phase Systems (ATPS). The integrated process was carried out to assess the production, partition and fibrinolytic enzyme recovery, according to a 2 3 -experimental design, using as independent variables Polyethylene glycol (PEG) molar mass, PEG and sodium sulphate concentration, concentration. The highest fibrinolytic activity (15.40U/mL) was obtained in sodium sulfate rich phase in the assay comprising of 10% of salt and 18% of PEG 8000 (g/mol). Yield greater than 80% was obtained. The fibrinolytic protease presented optimum pH 7.0 and stability between pH 6.0 and 8.5, and optimum temperature 50°C, stable between 10°C to 50°C. The enzyme was classified as a serine-protease with 52kDa of molecular weight. As a result, the process is remarkably effective to pre-purify the fibrinolytic protease with a low cost and significantly faster processing time. When compared to other isolated production and purification techniques the extractive fermentation is worthy of being a candidate to replace the initial stages of conventional separation processes.(AU)

Modification with CREKA Improves Cell Retention in a Rat Model of Myocardial Ischemia Reperfusion.

Poor cell homing limits the efficacy of cardiac cellular therapy. The homing peptide, cysteine-arginine-glutamic acid-lysine-alanine (CREKA), targets fibrin effectively which is involved in the repair process of tissue injury. Here, we assessed if CREKA-modified stem cells had enhanced fibrin-mediated homing ability resulting in better functional recovery and structural preservation in a rat myocardial injury model. CREKA-modified mesenchymal stem cells (CREKA-MSCs) were obtained via membrane fusion with CREKA-modified liposomes. The fibrin targeting ability of CREKA-MSCs was examined both in vitro and in vivo. Under both static and flow conditions in vitro, CREKA significantly enhanced MSCs binding ability to fibrin clots (2.6- and 2.3-fold, respectively). CREKA-MSCs showed 6.5-fold higher accumulation than unmodified MSCs in injured rat myocardium one day after administration, resulting in better structural preservation and functional recovery. Fibrin is, therefore, a novel target for enhancing homing of transplanted cells to injured myocardium, and the delivery system of fibrin-targeting is on behalf of a universalizable platform technology for regenerative medicine. Stem Cells 2019;37:663-676.

Rivaroxaban Promotes Reduction of Embolus Size within Cerebrocortical Microvessels in a Mouse Model of Embolic Stroke.

Previous reports have suggested that direct oral anticoagulants exert a prothrombolytic effect against intracardiac thrombi. We hypothesized that these anticoagulants may also help recanalize occluded intracranial arteries via prothrombolytic effects. In this study, we evaluated the effects of rivaroxaban, a direct oral anticoagulant, on fibrin emboli within the cerebrocortical microvessels in a mouse model of embolic stroke. Fibrin emboli prepared ex vivo were injected into the common carotid artery of male C57BL/6 mice, and embolization in the microvessels on the brain surface was observed through a cranial window. Oral administration of rivaroxaban was initiated a week before injection of the emboli. The number and sizes of the emboli were measured at two time points: immediately after and 3 h after the embolus injection in the rivaroxaban-treated mice (n =6) and untreated mice (n =7). The rates of recanalization and change in the embolus size were analyzed between the two groups. Complete recanalization was observed only in the rivaroxaban group (three mice in the rivaroxaban group compared with none in the control group). A significantly higher rate of reduction of the embolus size was observed in the rivaroxaban group than in the control group (P=0.0216). No significant differences between the two groups were observed in the serum levels of the following coagulation markers: thrombin-antithrombin III complexes, D-dimers, or plasmin-α2-plasmin inhibitor complex. Our findings indicate that rivaroxaban may promote reduction in the size of stagnated fibrin emboli in cerebrocortical microvessels in cases of embolic stroke.

Chemotherapy payload of anti-insoluble fibrin antibody-drug conjugate is released specifically upon binding to fibrin.

Cancer-induced blood coagulation in human tumour generates insoluble fibrin (IF)-rich cancer stroma in which uneven monoclonal antibody (mAb) distribution reduce the potential effectiveness of mAb-mediated treatments. Previously, we developed a mAb that reacts only with IF and not with fibrinogen (FNG) or the fibrin degradation product (FDP). Although IF, FNG and FDP share same amino acid sequences, the mAb is hardly neutralised by FNG and FDP in circulation and accumulates in fibrin clots within tumour tissue. Here, we created an antibody drug conjugate (ADC) using the anti-IF mAb conjugated with a chemotherapy payload (IF-ADC). The conjugate contains a linker severed specifically by plasmin (PLM), which is activated only on binding to IF. Imaging mass spectrometry showed the substantial intratumour distribution of the payload following the IF-ADC injection into mice bearing IF-rich 5-11 xenografts derived from pancreatic tumours of LSL-KrasG12D/+; LSL-Trp53R172H/+; Ptf1a-Cre (KPC) mice. IF-ADC treatment significantly extended the survival of the KPC mice. These data suggest that conjugating chemotherapy drugs to this IF-specific mAb could represent an effective means of treating stroma-rich tumours.

Favorable 2'-substitution in the loop region of a thrombin-binding DNA aptamer.

Simple 2'-OMe-chemical modification in the loop region of the 15mer G-rich DNA sequence GGTTGGTGTGGTTGG is reported. The G-quadruplex structure of this thrombin-binding aptamer (TBA), is stabilized by single modifications (T → 2'-OMe-U), depending on the position of the modification. The structural stability also renders significantly increased inhibition of thrombin-induced fibrin polymerization, a process closely associated with blood-clotting.

Assessment of the anti-snakebite properties of extracts of Aniba fragrans Ducke (Lauraceae) used in folk medicine as complementary treatment in cases of envenomation by Bothrops atrox.

ETHNOPHARMACOLOGICAL RELEVANCE: Extracts of leaves and bark of Aniba fragrans are used as tea (decoction) to treat snakebites in communities in the Brazilian Amazon. The aqueous extract of the leaves of A. fragrans has been proven to be effective against Bothrops venom, but only when pre-incubated with the venom. This study sought to assess the potential of different types of extract of this species to inhibit the biological activities of Bothrops atrox venom (BaV) when used the same way as in folk medicine. The main classes of secondary metabolites and the concentrations of phenolics in the extracts were also determined. MATERIALS AND METHODS: Four types of extract of A. fragrans were prepared: aqueous extract of the leaf (AEL), aqueous extract of the bark (AEB), hydroalcoholic leaf extract (HLE) and extract of the residue from hydrodistillation of the leaf (ERHL). The phytochemical profiles of the aqueous extracts were determined using thin layer chromatography (TLC), and the concentrations of phenolics were measured by colorimetric assays. To investigate the potential of the extracts to inhibit the biological activities of BaV, in vitro tests for antiphospholipase and antifibrinolytic activities were performed. In vivo tests for antihemorrhagic and antidefibrinating activities were also carried out, as well as antimicrobial tests for activity against the main bacteria found in the oral cavity of snakes. Interaction between the extracts and the proteins in BaV was assessed by electrophoresis (SDS-PAGE) and Western blot (WB). The cytotoxicity of the extracts was assessed in a strain of MRC-5 human fibroblasts. RESULTS: Terpenoids, flavonoids and condensed and hydrolysable tannins were detected in all the extracts. Metabolites such as coumarins, fatty acids and alkaloids were present in some extracts but not in others, indicating different phytochemical profiles. Phenolics content varied between extracts, and there were more tannins in AEB and HLE. In the in vitro tests, the extracts inhibited the phospholipase and fibrinolytic activities of BaV in the two ratios of venom to extract used. HLE exhibited effective antimicrobial action as it inhibited growth of 11 of the 15 bacteria investigated, including Morganella morganii, the main bacteria described in the oral cavity of snakes. The extracts failed to inhibit the defibrinating activity of BaV, and only the Bothrops antivenom had a significant effect (96.1%) on this activity. BaV-induced hemorrhage was completely inhibited by AEL and AEB when the pre-incubation (venom:extract) protocol was used. When administered orally, as in folk medicine, both AEB and AEL produced significant inhibition of hemorrhagic activity (maximum inhibition 46.5% and 39.2%, respectively). SDS-PAGE and WB of the extracts pre-incubated with BaV showed that the main proteins in the venom had been precipitated by the extracts. None of the four extracts showed cytotoxic effects in the tests carried out with a human fibroblast cell line. CONCLUSION: In addition to being effective in reducing hemorrhage when administered orally, the extracts displayed a high antimicrobial potential against microorganisms involved in secondary infections at the site of the snakebite. Once the extracts have been tested in accordance with the appropriate regulations, this species could potentially be used to produce a phytomedicine for complementary treatment of the secondary infections due to bacteria that aggravate the local signs and symptoms after snakebite envenomation.

The role of spinal thrombin through protease-activated receptor 1 in hyperalgesia after neural injury.

OBJECTIVE Painful neuropathic injuries induce blood-spinal cord barrier (BSCB) breakdown, allowing pro-inflammatory serum molecules to cross the BSCB, which contributes to nociception. The goal of these studies was to determine whether the blood-borne serine protease thrombin also crosses a permeable BSCB, contributing to nociception through its activation of protease-activated receptor-1 (PAR1). METHODS A 15-minute C-7 nerve root compression, which induces BSCB breakdown and painful behaviors by Day 1, was administered in the rat (n = 10); sham operation (n = 11) and a 3-minute compression (n = 10) that does not induce sensitivity were administered as controls. At Day 1 after root compression, spinal cord tissue was co-immunolabeled for fibrin/fibrinogen, the enzymatic product of thrombin, and IgG, a serum protein, to determine whether thrombin acts in areas of BSCB breakdown. To determine whether spinal thrombin and PAR1 contribute to hyperalgesia after compression, the thrombin inhibitor hirudin and the PAR1 antagonist SCH79797, were separately administered intrathecally before compression injuries (n = 5-7 per group). Rat thrombin was also administered intrathecally with and without SCH79797 (n = 6 per group) to determine whether spinal thrombin induces hypersensitivity in naïve rats through PAR1. RESULTS Spinal fibrin(ogen) was elevated at Day 1 after root compression in regions localized to BSCB breakdown and decreased in those regions by Day 7. Blocking either spinal thrombin or PAR1 completely prevented compression-induced hyperalgesia for 7 days. Intrathecal thrombin induced transient pain that was prevented by blocking spinal PAR1 before its injection. CONCLUSIONS The findings of this study suggest a potent role for spinal thrombin and its activation of PAR1 in pain onset following neuropathic injury.

Comparative Effect of Quercetin and Quercetin-3-O-ß-d-Glucoside on Fibrin Polymers, Blood Clots, and in Rodent Models.

The present study evaluates the in vitro, in vivo, and ex vivo antithrombotic and anticoagulant effect of two flavonoids: quercetin and quercetin-3-O-ß-d-glucoside (isoquercetin). The present results have shown that quercetin and isoquercetin inhibit the enzymatic activity of thrombin and FXa and suppress fibrin clot formation and blood clotting. The prolongation effect of quercetin and isoquercetin against epinephrine and collagen-induced platelet activation may have been caused by intervention in intracellular signaling pathways including coagulation cascade and aggregation response on platelets and blood. The in vivo and ex vivo anticoagulant efficacy of quercetin and isoquercetin was evaluated in thrombin-induced acute thromboembolism model and in ICR mice. Our findings showed that in vitro and in vivo inhibitory effects of quercetin were slightly higher than that of quercetin glucoside, whereas in vitro and ex vivo anticoagulant effects of quercetin were weaker than that of quercetin glucoside because of their structural characteristics.

Antithrombotic and antiplatelet activities of small-molecule alkaloids from Scolopendra subspinipes mutilans.

The aim of this study was to discover small-molecule anticoagulants from Scolopendra subspinipes mutilans (SSM). A new acylated polyamine (1) and a new sulfated quinoline alkaloid (2) were isolated from SSM. Treatment with the new alkaloids 1, 2, and indole acetic acid 4 prolonged the activated partial thromboplastin time and prothrombin time and inhibited the activity and production of thrombin and activated factor X. Furthermore, compounds 1, 2, and 4 inhibited thrombin-catalyzed fibrin polymerization and platelet aggregation. In accordance with these potential in vitro antiplatelet activities, compounds 1, 2, and 4 showed enhanced antithrombotic effects in an in vivo pulmonary embolism and arterial thrombosis model. Compounds 1, 2, and 4 also elicited anticoagulant effects in mice. Collectively, this study may serve as the groundwork for commercializing SSM or compounds 1, 2, and 4 as functional food components for the prevention and treatment of pathogenic conditions and serve as new scaffolds for the development of anticoagulants.

Spirulan from blue-green algae inhibits fibrin and blood clots: its potent antithrombotic effects.

We investigated in vitro and in vivo fibrinolytic and antithrombotic activity of spirulan and analyzed its partial biochemical properties. Spirulan, a sulfated polysaccharide from the blue-green alga Arthrospira platensis, exhibits antithrombotic potency. Spirulan showed a strong fibrin zymogram lysis band corresponding to its molecular mass. It specifically cleaved Aα and Bß, the major chains of fibrinogen. Spirulan directly decreased the activity of thrombin and factor X activated (FXa), procoagulant proteins. In vitro assays using human fibrin and mouse blood clots showed fibrinolytic and hemolytic activities of spirulan. Spirulan (2 mg/kg) showed antithrombotic effects in the ferric chloride (FeCl3 )-induced carotid arterial thrombus model and collagen and epinephrine-induced pulmonary thromboembolism mouse model. These results may be attributable to the prevention of thrombus formation and partial lysis of thrombus. Therefore, we suggest that spirulan may be a potential antithrombotic agent for thrombosis-related diseases.

Análisis comparativo de la regeneración ósea obtenida con quitosano y plasma rico en fibrina / Comparative analysis of the obtained bone regeneration with chitosan and plasma rich in fibrin

La regeneración ósea guiada (ROG) es un procedimiento que consiste en el incremento de la cantidad del hueso empleando materiales poliméricos biocompatibles como por ejemplo, el quitosano y el plasma rico en fibrina (PRF); los cuales se han valorado de manera individual con excelentes resultados. En este estudio, se propone analizar radiográficamente la regeneración ósea de ambos polímeros sobre alvéolos dentales postextracción. Se seleccionaron 5 pacientes con indicación de extracción de cordales inferiores bilaterales y a un alvéolo se aplicó quitosano y al otro PRF; se realizaron radiografías periapicales a los 15, 30, 60 y 120 días. Posteriormente, se analizaron las radiografías para observar el nivel de regeneración ósea y los resultados mostraron que ambos biomateriales regeneraron los tejidos, pero con la siguiente diferencia: la ROG con PRF ocurrió en menor tiempo mientras que la ROG con quitosano tuvo una mejor organización estructural. Se concluye que ambos biomateriales se pueden tomar como opciones de tratamientos en la regeneración ósea guiada de tejidos.

The bone regeneration it a procedure that consists in the formation of new bony tissues using biocompatible polymeric materials, among them the chitosan (natural biopolymer) and the rich fibrin plasma (PRF) this biomaterials have been studied and used to achieve the bony regeneration obtaining excellent results. The aim of this research was to design an experiment that allowing us to compare the regenerator effect of both polymers, after the extraction of dental pieces in human beings, using periapical radiography's. Five patients, with indication of extraction of the lower bilateral wisdom dental pieces were selected. Chitosan and PRF were applied on different dental sockets after surgery. To register the information, periapical Rx were taken and analyzed, the procedure were done monthly, for 120 days. The results for Rx showed that both biomaterials regenerated bony tissue. The PRF generated major quantity of tissue in minor time whereas the chitosan did it with better structural organization, so, it was possible to conclude that chitosan and PRF represents interesting options for the treatments where guided bony regeneration is required.

Adhesins of Leptospira interrogans mediate the interaction to fibrinogen and inhibit fibrin clot formation in vitro.

We report in this work that Leptospira strains, virulent L. interrogans serovar Copenhageni, attenuated L. interrogans serovar Copenhageni and saprophytic L. biflexa serovar Patoc are capable of binding fibrinogen (Fg). The interaction of leptospires with Fg inhibits thrombin- induced fibrin clot formation that may affect the haemostatic equilibrium. Additionally, we show that plasminogen (PLG)/plasmin (PLA) generation on the surface of Leptospira causes degradation of human Fg. The data suggest that PLA-coated leptospires were capable to employ their proteolytic activity to decrease one substrate of the coagulation cascade. We also present six leptospiral adhesins and PLG- interacting proteins, rLIC12238, Lsa33, Lsa30, OmpL1, rLIC11360 and rLIC11975, as novel Fg-binding proteins. The recombinant proteins interact with Fg in a dose-dependent and saturable fashion when increasing protein concentration was set to react to a fix human Fg concentration. The calculated dissociation equilibrium constants (K D ) of these reactions ranged from 733.3 ± 276.8 to 128 ± 89.9 nM for rLIC12238 and Lsa33, respectively. The interaction of recombinant proteins with human Fg resulted in inhibition of fibrin clot by thrombin-catalyzed reaction, suggesting that these versatile proteins could mediate Fg interaction in Leptospira. Our data reveal for the first time the inhibition of fibrin clot by Leptospira spp. and presents adhesins that could mediate these interactions. Decreasing fibrin clot would cause an imbalance of the coagulation cascade that may facilitate bleeding and help bacteria dissemination.

Cross-modulatory effects of clopidogrel and heparin on platelet and fibrin incorporation in thrombosis.

Pharmacologic inhibition of platelet activation and aggregation is a mainstay for reducing the incidence of arterial thrombosis, whereas anticoagulation is the primary approach for preventing the development of venous thrombosis. The effect of standard pharmacologic agents on their reciprocal vessel - anticoagulants on arterial thrombosis and platelet inhibitor on venous thrombosis - is relatively understudied. This study was designed to evaluate murine large-vessel arterial or venous thrombosis under conditions of either fibrin or platelet inhibition. In this study, heparin and clopidogrel were used as standard anticoagulant and platelet inhibitor, respectively, evaluating both large artery and vein thrombosis in mice, using in-vivo fluorescence imaging to simultaneously measure fibrin and platelet levels at the thrombus induction site. Heparin reduced both fibrin and platelet development in both arteries and veins, with stronger influences on fibrin accrual. Clopidogrel had a stronger effect in arteries, reducing both platelet and fibrin accumulation. Clopidogrel also reduced platelet accumulation with venous thrombosis, but the reductions in fibrin formation did not reach statistical significance. These findings illustrate the interactive role of platelet activity and coagulation in the development of large-vessel thrombosis, with inhibition of one thrombotic component showing profound effects on the other component in both arterial and venous thrombosis.

A fibrinogen concentrate Haemocomplettan (Riastap) or a Factor XIII concentrate Fibrogammin combined with a mini dose of tranexamic acid can reverse the fibrin instability to fibrinolysis induced by thrombin- or FXa-inhibitor.

To assess whether Haemocomplettan(®) (fibrinogen concentrate) or Fibrogammin(®) (Factor XIII concentrate) can be used to manage bleeding complications of antithrombotic treatment, we examined a normal plasma pool spiked with AR-H067637 (thrombin inhibitor) or rivaroxaban (activated factor X-inhibitor), to which one of the concentrates was added. Fibrin network permeability (Ks), images of Scanning Electron Microscopy (SEM) and Clot Lysis Time (CLT) were examined. Both inhibitors increased the Ks levels, which could be fully or partly reversed by Haemocomplettan(®) or Fibrogammin(®) respectively. However, these modified clots with tightened network remained non-resistant to fibrinolysis, shown as unaffected CLT. Tranexamic acid at a very low concentration (0·4 mg/ml) aided the two concentrates to stabilize the clots, where the prolongation of CLT was more pronounced for a lower dose than a higher dose of Haemocomplettan(®) while Fibrogammin(®) brought the greatest delay to CLT out of all additions. These observations were partly supported by SEM images, displaying alterations of fibrin fibre arrangement known to influence fibirinolysis. The in vitro data suggest that Haemocomplettan(®) or Fibrogammin(®) given in combination with a mini dose of tranexamic acid may slow down the natural clearance of fibrin clot by plasmin and thus prevent patients from haemorrhagic complications during antithrombotic therapy.

[Dependence of the anticoagulant activity of starch and inulin on their degree of sulfonation].

We have studied a relationship between the degree of sulfonation and anticoagulant activity of starch from Solanum tuberosum (molecular weight, 25000-30000 Da; sulfonation degree, 0.4-2.5) and inulin from Helianthus tuberosus (molecular weight, 7000-8000 Da; sulfonation degree, 0.6-1.6). Starch and inulin sulfates (i) increased the time of appearance of fibrin clots in plasma in coagulometric tests and (ii) reduced (via antithrombin) the rate of thrombin-induced hydrolysis of a chromogen substrate. The antithrombin (aIIa) activity of starch sulfates reached 16.8-70.0 IU/mg and the activity against factor Xa (aXa activity) was 2.3-16.6 IU/mg. The antithrombin activity of inulin sulfates was within 5.5-11.4 IU/mg and the activity against factor Xa (aXa activity) was within 0-1.4 IU/mg. An increase in the degree of sulfonation led to a growth in the anticoagulant activity of starch sulfates. The anticoagulant activity of starch sulfates and inulin sulfate with sulfonation degree 1.0 is mediated by antithrombin, which is the plasma inhibitor of serine proteases.