Thrombin-activatable Inhibitor Research Articles

Inhibition of prostaglandin E2 receptor EP3 mitigates thrombin-induced brain injury

Prostaglandin E2 EP3 receptor is the only prostaglandin E2 receptor that couples to multiple G-proteins, but its role in thrombin-induced brain injury is unclear. In the present study, we exposed mouse hippocampal slice cultures to thrombin in vitro and injected mice with intrastriatal thrombin in vivo to investigate the role of EP3 receptor in thrombin-induced brain injury and explore its underlying cellular and molecular mechanisms. In vitro, EP3 receptor inhibition reduced thrombin-induced hippocampal CA1 cell death. In vivo, EP3 receptor was expressed in astrocytes and microglia in the perilesional region. EP3 receptor inhibition reduced lesion volume, neurologic deficit, cell death, matrix metalloproteinase-9 activity, neutrophil infiltration, and the number of CD68+ microglia, but increased the number of Ym-1+ M2 microglia. RhoA-Rho kinase levels were increased after thrombin injection and were decreased by EP3 receptor inhibition. In mice that received an intrastriatal injection of autologous arterial blood, inhibition of thrombin activity with hirudin decreased RhoA expression compared with that in vehicle-treated mice. However, EP3 receptor activation reversed this effect of hirudin. These findings show that prostaglandin E2 EP3 receptor contributes to thrombin-induced brain damage via Rho-Rho kinase–mediated cytotoxicity and proinflammatory responses.

Synthesis of scutellarein derivatives to increase biological activity and water solubility

In order to improve the biological activity and water solubility of scutellarin (1), some derivatives of its main metabolite (scutellarein) were designed and synthesized. All the compounds were tested for their thrombin inhibition activity through the analyzation of thrombin time (TT), activated partial thromboplastin time (APTT), prothrombin time (PT) and fibrinogen (FIB). Their antioxidant activities were assessed by measuring their scavenging capacities toward 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and the ability to protect PC12 cells against H2O2-induced cytotoxicity, their water solubility were also assessed by ultraviolet (UV) spectrophotometer. The results showed that compound 8b demonstrated stronger anticoagulant and antioxidant activity, better water solubility compared with scutellarein (2), which warrants it as a promising agent for the treatment of ischemic cerebrovascular disease.

잎새버섯 물추출물 및 유기용매 분획물의 생리활성

잎새버섯으로 준비된 물 추출물과 유기용매 분획물의 혈전용해활성과 트롬빈저해활성, acetylcholinesterase 저해활성, 항산화활성 및 면역활성을 확인하였다. 물 추출물과 물 분획물은 각각 1.55 plasmin unit와 0.85 plasmin unit의 높은 혈전용해활성을 나타내고, 물 분획물과 에틸 아세테이트 분획물은 76.43%와 72.59%의 트롬빈저해활성을 나타냈다. 클로로포름 분획물과 헥산 분획물이 95.14%와 94.74%의 높은 acetylcholinesterase 저해활성을 나타냈으며, 부탄올 분획물과 물 추출물이 94.47%와 91.04%의 항산화활성을 나타냈다. 부탄올 분획물과 물 분획물이 각각 2배 이상의 높은 면역기능활성을 나타냈다. 실험 결과로부터 잎새버섯의 분획물은 높은 혈전용해활성, 트롬빈 저해활성, acetylcholinesterase 저해활성 및 면역 기능활성을 나타내 심혈관계 질환과 치매의 예방 및 면역 기능강화를 위한 기능성식품 개발에 이용할 수 있을 것으로 사료된다. This study was performed in order to analyze the fibrinolytic, thrombin inhibitory, anti-oxidative, acetylcholinesterase inhibitory, and immuno-enhancing activities of the water extract and solvent fractions isolated from Grifola frondosa. Fibrinolytic activity was analyzed using the fibrin plate method, and thrombin inhibitory activity was assayed using the substrate H-D-Phe-piparg- pna. Anti-oxidative activity was estimated using the DPPH assay, and AChE inhibitory activity was measured using the spectrophotometric method. Immuno-enhancing activity was examined using the nitric oxide (NO) production in RAW 264.7 macrophage cells. Cell viability was determined using the MTS assay. Fibrinolytic activities were the highest in water extract (1.55 plasmin units/mL) followed by water fraction (0.85 plasmin units/mL). The thrombin inhibitory activities of the water and ethyl acetate fractions were determined to be 76.43% and 72.59%, respectively. The acetylcholinesterase inhibitory activities of chloroform and hexane fractions exhibited values of 95.14% and 94.74%, respectively. The butanol fraction showed the highest anti-oxidative activity at 94.47%. Anti-proliferating activity against Raw 264.7 cells showed no cytotoxicity. The production of NO in Raw 264.7 cells increased up to 2-fold by adding the water fraction compared to the untreated control. These results suggest that Grifola frondosa may serve as a useful functional food for the enhancement of immune function and the prevention and therapy of cardiovascular diseases.

Design, synthesis, biological evaluation and molecular docking studies of dabigatran analogs as potential thrombin inhibitors

A series of fluorinated dabigatran analogs were designed and synthesized. All the target compounds were characterized by 1H NMR, 13C NMR, and FT-ICR-MS. The thrombin inhibitory activities of the new synthesized compounds were also evaluated in vitro. The results show that compound 12a has the highest IC50 of thrombin inhibition (IC50 = 5.41 nM). Moreover, molecular docking simulation was carried out to elucidate the conformations of the compounds and key amino acid residues at the active site of thrombin protein. The results show there is an appropriate relationship between IC50 and the docking scores for compounds 12a–e. We suggest that the hydrogen bond interaction between Asp189, Gly219 of thrombin and the compounds appear to play major role in thrombin inhibition.

Triterpenoid profile and bioactivity study of Oenothera maritima

Four new triterpenoids, 2α,3α,20β,23-tetrahydroxy-ursa-12,19(29)-dien-28-oic acid (1), 2α,3α,20β,23-tetrahydroxy-ursa-12,19(29)-dien-28,20β-lactone (2), 2α,3α-dihydroxy-ursa-12,19-dien-28-oic acid 28-O-β-d-glucopyranoside (3) and 2α,3α,23-trihydroxy-ursa-12,19(29)-dien-28-oic acid (4) together with six known compounds (5–10), were isolated from the aerial parts of Oenothera maritima Nutt. Their structures were elucidated on the basis of spectroscopic data and chemical methods. Compounds 1, 3–10 were evaluated for their in vitro thrombin inhibitory activity and their selectivity against factor Xa and trypsin.

Effect of the oral thrombin inhibitor dabigatran on allergic lung inflammation induced by repeated house dust mite administration in mice.

Asthma is a chronic disease of the airways; asthma patients are hampered by recurrent symptoms of dyspnoea and wheezing caused by bronchial obstruction. Most asthma patients suffer from chronic allergic lung inflammation triggered by allergens such as house dust mite (HDM). Coagulation activation in the pulmonary compartment is currently recognized as a feature of allergic lung inflammation, and data suggest that coagulation proteases further drive inflammatory mechanisms. Here, we tested whether treatment with the oral thrombin inhibitor dabigatran attenuates allergic lung inflammation in a recently developed HDM-based murine asthma model. Mice were fed dabigatran (10 mg/g) or placebo chow during a 3-wk HDM airway exposure model. Dabigatran treatment caused systemic thrombin inhibitory activity corresponding with dabigatran levels reported in human trials. Surprisingly, dabigatran did not lead to inhibition of HDM-evoked coagulation activation in the lung as measured by levels of thrombin-antithrombin complexes and D-dimer. Repeated HDM administration caused an influx of eosinophils and neutrophils into the lungs, mucus production in the airways, and a T helper 2 response, as reflected by a rise in bronchoalveolar IL-4 and IL-5 levels and a systemic rise in IgE and HDM-IgG1. Dabigatran modestly improved HDM-induced lung pathology (P < 0.05) and decreased IL-4 levels (P < 0.01), without influencing other HDM-induced responses. Considering the limited effects of dabigatran in spite of adequate plasma levels, these results argue against clinical evaluation of dabigatran in patients with asthma.

The Anticoagulation Effects of Glycosaminoglycan from &lt;em&gt;Mactra veneriformis&lt;/em&gt;

In this study, the anticoagulation effect of glycosaminoglycan from <em>Mactra veneriformis</em> was studied. The results showed that glycosaminoglycan mainly exerted anticoagulation via antithrombin III. Glycosaminoglycan could passivate the function of heparin cofactor II inhibiting thrombin activity. Glycosaminoglycan significantly reduced the activities of coagulation factor II, V, VII, X, VIII, IX, XI, XII as well as fibrinogen content in the plasma (p<0.05, p<0.01). Besides, glycosaminoglycan could extend blood recalcification time in rats by shielding Ca²⁺ in plasma and significantly reduced Ca²⁺ concentration in rats and mice serum (p<0.05, p<0.01). Glycosaminoglycan reduced the Ca2+ concentration in serum in a more intensive way than that of heparin sodium (p<0.05, p<0.01).

Discovery of non-competitive thrombin inhibitor derived from competitive tryptase inhibitor skeleton: Shift in molecular recognition resulted from skeletal conversion of carboxylate into phosphonate.

A novel series of terminal and internal phosphonate esters based on our previously developed aryl carboxylate-type tryptase selective inhibitor 1 was synthesized. The potency of these synthesized compounds was assessed in vitro with an enzyme inhibition assay using three available serine proteases, that is, tryptase, trypsin, and thrombin. The internal phosphonate derivative 6 showed potent thrombin inhibitory activity with an IC50 value of 1.0 μM, whereas it exhibited no or only weak tryptase and trypsin inhibition at 10 μM. The Lineweaver-Burk plot analysis indicates that the inhibition pattern of thrombin with 6 is non-competitive in spite of the fact that the lead carboxylate compound 1 is competitive inhibitor. Therefore, the skeletal conversion of the carboxylate into a phosphonate alters the mode of molecular recognition of these inhibitors by thrombin.

Development of Orally Active Thrombin Inhibitors for the Treatment of Thrombotic Disorder Diseases

Thrombotic disorders represent the major share of the various cardiovascular diseases, and significant progress has been made in the development of synthetic thrombin inhibitors as new anticoagulants. In addition to the development of highly potent and selective inhibitors with improved safety and suitable half-life, several allosteric inhibitors have been designed and synthesized, that did not fully nullify the procoagulant signal and thus could result in reduced bleeding complications. Furthermore, natural products with thrombin inhibitory activity have been isolated, and some natural products have been modified in order to improve their inhibitory activity and metabolic stability. This review summarizes the development of orally active thrombin inhibitors for the treatment of thrombotic disorder diseases, which could serve as a reference for the interested researchers.

Synthesis and biological evaluation of novel dabigatran derivatives as thrombin inhibitors

A novel series of 3-[{2-[(4-carbamimidoylphenylamino)methyl]-1-substituted-1H-benzoimidazole-5-carbonyl}(3-chloro-4-fluorophenyl)amino]propionic derivatives of dabigatran was synthesized. The structures of the compounds were characterized by 1H NMR, 13C NMR, HRMS, and elemental analysis. The compounds were screened for in vitro thrombin inhibitory activity. The results indicated that the compounds had low to moderate inhibitory activity. The compounds with N-methyl and N-ethyl side chains had much greater inhibitory activity against thrombin than those with other side chains.

Design, synthesis and structural exploration of novel fluorinated dabigatran derivatives as direct thrombin inhibitors

Twenty-one fluorinated dabigatran derivatives were designed based on the bioisosteric principle. All derivatives were synthesised and evaluated for their thrombin inhibitory activity in vitro. Among these compounds, 14h, 14m, 14s and 14t were potent and the activity was in the range of reference drug, dabigatran. Three structural changes were introduced in these 21 compounds to elucidate the structure–activity relationship of the drugs. In addition, prodrugs of compounds 14h and 14s were developed to investigate their anticoagulant activities in vivo. In these experiments, compound 16 showed a fairly strong inhibitory effect on thrombin-induced platelet aggregation, and demonstrated potent activity for inhibiting arteriovenous thrombosis with an inhibition rate of (73 ± 6) %, which was comparable to that of dabigatran etexilate (76 ± 2) %. Moreover, molecular docking studies were performed to understand the binding interactions of active compounds 14h, 14s and 14t with thrombin protein (PDB ID:1KTS). Contour maps obtained from the 3D-QSAR model are meaningful in designing more active molecules to act as direct inhibitors of thrombin.

Prediction of thrombin and factor xa inhibitory activity with associative neural networks.

Quantitative structure-activity relationship studies on a series of selective inhibitors of thrombin and factor Xa were performed by using Associative Neural Network. To overcome the problem of overfitting due to descriptor selection, 5-fold cross-validation with variable selection in each step of the analysis was performed. The predictive ability of the models was tested through leave-one-out cross-validation, giving a Q2=0.74-0.87 for regression models. Predictions for the external evaluation sets obtained accuracies in the range of 0.71-0.82 for regressions. The proposed models can be potential tools for finding new drug candidates.

Screening of direct thrombin inhibitors from Radix Salviae Miltiorrhizae by a peak fractionation approach

Thrombin plays a significant role in thromboembolic disease. In this work, a peak fractionation approach combined with an activity assay method was used to screen direct thrombin inhibitors from Radix Salviae Miltiorrhizae (RSM), a famous herbal remedy for the treatment of cardiovascular diseases in China. A total of 91 fractions were collected from the RSM extract, and 19 fractions out of them showed thrombin inhibitory effects with dose–effect relationship. Among them, three compounds were unambiguously identified as 15, 16-dihydrotanshinone I, cryptotanshinone and tanshinone IIA with IC50 values of 29.39, 81.11 and 66.60μM, respectively. The three compounds were reported with direct thrombin inhibition activities for the first time and their ligand–thrombin interactions were explored by a molecular docking research. These results may contribute to explain the medical benefit of RSM for the prevention and treatment of cardiovascular diseases.

GTM-Based QSAR Models and Their Applicability Domains.

In this paper we demonstrate that Generative Topographic Mapping (GTM), a machine learning method traditionally used for data visualisation, can be efficiently applied to QSAR modelling using probability distribution functions (PDF) computed in the latent 2-dimensional space. Several different scenarios of the activity assessment were considered: (i) the "activity landscape" approach based on direct use of PDF, (ii) QSAR models involving GTM-generated on descriptors derived from PDF, and, (iii) the k-Nearest Neighbours approach in 2D latent space. Benchmarking calculations were performed on five different datasets: stability constants of metal cations Ca(2+) , Gd(3+) and Lu(3+) complexes with organic ligands in water, aqueous solubility and activity of thrombin inhibitors. It has been shown that the performance of GTM-based regression models is similar to that obtained with some popular machine-learning methods (random forest, k-NN, M5P regression tree and PLS) and ISIDA fragment descriptors. By comparing GTM activity landscapes built both on predicted and experimental activities, we may visually assess the model's performance and identify the areas in the chemical space corresponding to reliable predictions. The applicability domain used in this work is based on data likelihood. Its application has significantly improved the model performances for 4 out of 5 datasets.

Biochemical characterization of prothrombin complex concentrates in China

Despite increasing use of prothrombin complex concentrates (PCCs), there is little knowledge about the biochemical characterization of Chinese PCCs. Six Chinese PCCs were investigated and compared with PCCs (Octaplex®) from Europe. The levels of coagulation factors and inhibitors were detected. The presence of activated coagulation factors was assessed. Furthermore, their thrombin inhibitory capacities, specific activity and purity were assayed. All above parameters of biochemical properties were statistically analyzed.Chinese PCCs contained FⅡ, Ⅶ, Ⅸ and Ⅹ, protein C, S and Z, heparin and extremely low level antithrombin, as well as Octaplex®. The measured FⅨ activities were similar to those declared, however the measured potency of FⅡ, Ⅶ and Ⅹ greatly exceeded the labeled. Though all preparations were negative for activated coagulation factors in non-activated partial thromboplastin time test, the activated coagulation factor Ⅶ (FⅦa) remained in all PCCs and its content differed greatly. Overall, FⅦa content of Chinese PCCs was higher than that of Octaplex®. Further, Chinese PCCs were inferior to Octaplex® in the thrombin inhibitory capacities, specific activity and purity. In summary, compared with Octaplex®, Chinese PCCs' errors about the labeled activity of coagulation factors and probably high risks of thrombosis should be considered.

Heparin cofactor II is degraded by heparan sulfate and dextran sulfate

Heparan sulfate normally binds to heparin cofactor II and modulates the coagulation pathway by inhibiting thrombin. However, when human heparin cofactor II was incubated with heparan sulfate, heparin cofactor II became degraded. Other glycosaminoglycans were tested, including hyaluronic acid, chondroitin sulfates, dermatan sulfate, and heparin, but only dextran sulfate also degraded heparin cofactor II. Pretreatment of heparan sulfate with heparinase reduced its heparin cofactor II-degrading activity. Heparan sulfate and dextran sulfate diminished the thrombin inhibitory activity of heparin cofactor II. Other serpins, including antithrombin III and pigment epithelium-derived factor, were also degraded by heparan sulfate. This is the first evidence of acidic polysaccharides exhibiting protein-degrading activity without the aid of other proteins.

Anticoagulant mechanism and platelet deaggregation property of a non-cytotoxic, acidic phospholipase A2 purified from Indian cobra (Naja naja) venom: inhibition of anticoagulant activity by low molecular weight heparin.

In the present study, anticoagulant and platelet modulating activities of an acidic phospholipase A2 (NnPLA2-I) purified from Indian cobra Naja naja venom was investigated. The NnPLA2-I displayed a mass of 15.2 kDa and 14,186.0 Da when analyzed by SDS-PAGE and MALDI-TOF-MS, respectively. Peptide mass fingerprinting analysis of the NnPLA2-I showed its significant similarity with phospholipase A2 enzymes purified from cobra venom. BLAST analysis of one tryptic peptide sequence of NnPLA2-I demonstrated putative conserved domains of the PLA2-like superfamily. The Km and Vmax values of NnPLA2-I toward hydrolysis of its most preferred substrate-phosphotidylcholine (PC)-were determined to be 0.72 mM and 29.3 μmol min(-1) mg(-1), respectively. The anticoagulant activity of NnPLA2-I was found to be higher than the anticoagulant activity of heparin/AT-III or warfarin. The histidine modifying reagent, monovalent and polyvalent antivenom differentially inhibited the catalytic and anticoagulant activities of NnPLA2-I. Low molecular weight heparin did not inhibit the catalytic and platelet deaggregation activity of NnPLA2-I, albeit its anticoagulant activity was significantly reduced. The NnPLA2-I showed a non-enzymatic, mixed inhibition of thrombin with a Ki value of 9.3 nM. Heparin significantly decreased, with an IC50 value of 15.23 mIU, the thrombin inhibitory activity of NnPLA2-I. The NnPLA2-I uniquely increased the amidolytic activity of FXa without influencing its prothrombin activating property. NnPLA2-I showed dose-dependent deaggregation of platelet rich plasma (PRP) and inhibited the collagen and thrombin-induced aggregation of PRP. However, deaggregation of washed platelets by NnPLA2-I demonstrated in presence of PC or platelet poor plasma. Alkylation of histidine residue of NnPLA2-I resulted in 95% and 21% reduction of its platelet deaggregation and platelet binding properties, respectively. NnPLA2-I did not show cytotoxicity against human glioblastoma U87MG cells, bactericidal or hemolytic activity. The future therapeutic application of NnPLA2-I for treatment and prevention of cardiovascular disorders is therefore suggested.

Structural basis of RGD-hirudin binding to thrombin: Tyr3 and five C-terminal residues are crucial for inhibiting thrombin activity.

BackgroundHirudin is an anti-coagulation protein produced by the salivary glands of the medicinal leech Hirudomedicinalis. It is a powerful and specific thrombin inhibitor. The novel recombinant hirudin, RGD-hirudin, which contains an RGD motif, competitively inhibits the binding of fibrinogen to GPIIb/IIIa on platelets, thus inhibiting platelet aggregation while maintaining its anticoagulant activity.ResultsRecombinant RGD-hirudin and six mutant variants (Y3A, S50A, Q53A, D55A, E57A and I59A), designed based on molecular simulations, were expressed in Pichia pastoris. The proteins were refolded and purified to homogeneity as monomers by gel filtration and anion exchange chromatography. The anti-thrombin activity of the six mutants and RGD-hirudin was tested. Further, we evaluated the binding of the mutant variants and RGD-hirudin to thrombin using BIAcore surface plasmon resonance analysis (SPR). Kinetics and affinity constants showed that the KD values of all six mutant proteins were higher than that of RGD-hirudin.ConclusionsThese findings contribute to a novel understanding of the interaction between RGD-hirudin and thrombin.

검은비늘버섯 물 추출물 및 유기용매 분획물의 생리활성 효과

Department of Fine Chemistry and New Materials, Sangji University, Wonju 220-702, KoreaABSTRACT: This study was conducted in order to investigate the physiological activities, including antioxidative, fibrinolytic,thrombin inhibitory, and α-glucosidase inhibitory activities of the water extract and solvent fractions isolated from Pholiotaadiposa. The antioxidative activities of the water extract and water fraction were 57.57% and 48.27%, respectively. The fibrinolyticactivity was strong only in the ethyl acetate fraction at 0.70 plasmin units/mL. The ethyl acetate fraction showed high thrombininhibitory activity, and a-glucosidase inhibitory activity at 77.67% and 89.32%, respectively. The ethyl acetate fraction hydrolyzedboth Aα and Bβ subunits of human fibrinogen, but did not show reactivity for the γ form of human fibrinogen. Fibrinolytic activityof the ethyl acetate fraction was not decreased by heating for 10 min at 100

Molecular mimicry between dengue virus and coagulation factors induces antibodies to inhibit thrombin activity and enhance fibrinolysis.

Dengue virus (DENV) is the most common cause of viral hemorrhagic fever, and it may lead to life-threating dengue hemorrhagic fever and shock syndrome (DHF/DSS). Because most cases of DHF/DSS occur in patients with secondary DENV infection, anti-DENV antibodies are generally considered to play a role in the pathogenesis of DHF/DSS. Previously, we have found that antithrombin antibodies (ATAs) with both antithrombotic and profibrinolytic activities are present in the sera of dengue patients. However, the mechanism by which these autoantibodies are induced is unclear. In this study, we demonstrated that antibodies induced by DENV immunization in mice and rabbits could bind to DENV antigens as well as to human thrombin and plasminogen (Plg). The binding of anti-DENV antibodies to thrombin and Plg was inhibited by preadsorption with DENV nonstructural protein 1. In addition, affinity-purified ATAs from DENV-immunized rabbit sera could inhibit thrombin activity and enhance Plg activation both in vitro and in vivo. Taken together, our results suggest that molecular mimicry between DENV and coagulation factors can induce the production of autoantibodies with biological effects similar to those of ATAs found in dengue patients. These coagulation-factor cross-reactive anti-DENV antibodies can interfere with the balance of coagulation and fibrinolysis, which may lead to the tendency of DHF/DSS patients to bleed. Dengue virus (DENV) infection is the most common mosquito-borne viral disease in tropical and subtropical areas. Over 50 million DENV infection cases develop each year, and more than 2.5 billion people are at risk of dengue-induced hemorrhagic fever and shock syndrome. Currently, there is no vaccine or drug treatment for DENV. In the present study, we demonstrated that DENV immunization could induce thrombin and plasminogen (Plg) cross-reactive antibodies, which were able to inhibit thrombin activity and enhance Plg activation. These results suggest that molecular mimicry between DENV antigens, thrombin, and Plg may elicit antibodies that disturb hemostasis. The selection of appropriate candidate antigens for use in DENV vaccines should prevent these potentially dangerous autoimmune responses.