Carbamylation of Integrin α IIb ß 3: The Mechanistic Link to Platelet Dysfunction in ESKD.

BACKGROUND: Bleeding diatheses, common among patients with ESKD, can lead to serious complications, particularly during invasive procedures. Chronic urea overload significantly increases cyanate concentrations in patients with ESKD, leading to carbamylation, an irreversible modification of proteins and peptides. METHODS: To investigate carbamylation as a potential mechanistic link between uremia and platelet dysfunction in ESKD, we used liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify total homocitrulline, and biotin-conjugated phenylglyoxal labeling and Western blot to detect carbamylated integrin α IIb ß 3 (a receptor required for platelet aggregation). Flow cytometry was used to study activation of isolated platelets and platelet-rich plasma. In a transient transfection system, we tested activity and fibrinogen binding of different mutated forms of the receptor. We assessed platelet adhesion and aggregation in microplate assays. RESULTS: Carbamylation inhibited platelet activation, adhesion, and aggregation. Patients on hemodialysis exhibited significantly reduced activation of α IIb ß 3 compared with healthy controls. We found significant carbamylation of both subunits of α IIb ß 3 on platelets from patients receiving hemodialysis versus only minor modification in controls. In the transient transfection system, modification of lysine 185 in the ß 3 subunit was associated with loss of receptor activity and fibrinogen binding. Supplementation of free amino acids, which was shown to protect plasma proteins from carbamylation-induced damage in patients on hemodialysis, prevented loss of α IIb ß 3 activity in vitro. CONCLUSIONS: Carbamylation of α IIb ß 3-specifically modification of the K185 residue-might represent a mechanistic link between uremia and dysfunctional primary hemostasis in patients on hemodialysis. The observation that free amino acids prevented the carbamylation-induced loss of α IIb ß 3 activity suggests amino acid administration during dialysis may help to normalize platelet function.

Investigating the hemostatic effect of medicinal plant Arnebia euchroma (Royle) I.M.Johnst extract in a mouse model.

ETHNOPHARMACOLOGICAL RELEVANCE: Arnebia euchroma (Royle) I.M.Johnst (AE) has been reported to be a potentially useful medicinal herb for the treatment of several circulatory diseases in traditional Chinese medicine. It shows effects such as "cooling of the blood," promotion of blood circulation, detoxification, and rash clearance. AIM OF THE STUDY: To explore the hemostatic effect of the ethyl acetate extract of AE in mice. MATERIALS AND METHODS: In this study, we explored the effects of AE on bleeding time, blood coagulation time, platelet count, and blood coagulation parameters in normal Kunming mice. Different doses of the AE extract (5, 10, and 20 g kg-1·day-1) were administered to mice for 14 days. Sodium carboxymethyl cellulose (CMC-Na at 0.5%) and Yunnan Baiyao (0.8 g kg-1·day-1) were administered as negative and positive control treatments, respectively. Bleeding time, blood coagulation time, platelet count, blood platelet aggregation, blood platelet adhesion to fibrinogen, platelet factor 4 (PF-4) secretions from blood platelets, and blood coagulation parameters including prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen (FIB) levels were measured on day 15 of administration. RESULTS: Bleeding and blood coagulation time were significantly lower and TT was shorter in the AE extract-treated groups than in the control groups. Furthermore, FIB levels and platelet count were higher, whereas blood platelet aggregation, blood platelet adhesion to fibrinogen, and PF-4 secretion from blood platelets were more obvious in the AE extract-treated groups than in the control group. However, no significant differences were detected for PT and aPTT between the extract-treated and control groups. CONCLUSIONS: The ethyl acetate extract of AE showed potential hemostasis effects in mice by shortening the bleeding and coagulation time. In addition, the extract increased platelet count and induced blood platelet aggregation, blood platelet adhesion to fibrinogen, PF-4 secretion from blood platelets, and FIB level, while it shortened TT.

Stem Bromelain Proteolytic Machinery: Study of the Effects of its Components on Fibrin (ogen) and Blood Coagulation.

BACKGROUND: Antiplatelet, anticoagulant and fibrinolytic activities of stem bromelain (EC 3.4.22.4) are well described, but more studies are still required to clearly define its usefulness as an antithrombotic agent. Besides, although some effects of bromelain are linked to its proteolytic activity, few studies were performed taking into account this relationship. OBJECTIVE: We aimed at comparing the effects of stem bromelain total extract (ET) and of its major proteolytic compounds on fibrinogen, fibrin, and blood coagulation considering the proteolytic activity. METHODS: Proteolytic fractions chromatographically separated from ET (acidic bromelains, basic bromelains, and ananains) and their irreversibly inhibited counterparts were assayed. Effects on fibrinogen were electrophoretically and spectrophotometrically evaluated. Fibrinolytic activity was measured by the fibrin plate assay. The effect on blood coagulation was evaluated by the prothrombin time (PT) and activated partial thromboplastin time (APTT) tests. Effects were compared with those of thrombin and plasmin. RESULTS: Acidic bromelains and ananains showed thrombin-type activity and low fibrinolytic activity, with acidic bromelains being the least effective as anticoagulants and fibrinolytics; while basic bromelains, without thrombin-like activity, were the best anticoagulant and fibrinolytic proteases present in ET. Procoagulant action was detected for ET and its proteolytic compounds by the APTT test at low concentrations. The measured effects were dependent on proteolytic activity. CONCLUSION: Two sub-populations of cysteine proteases exhibiting different effects on fibrin (ogen) and blood coagulation are present in ET. Using well characterized stem bromelain regarding its proteolytic system is a prerequisite for a better understanding of the mechanisms underlying the bromelain action.

Characterisation of the binding of dihydro-alpha-lipoic acid to fibrinogen and the effects on fibrinogen oxidation and fibrin formation.

A reduced form of the alpha-lipoic acid, dihydro-alpha-lipoic acid (DHLA) is a potent, naturally occurring antioxidant which can be consumed as food constituent or as supplement at doses up to 600 mg/day. DHLA has inhibitory effect on coagulation as it can reduce concentrations of some coagulation factors. In this study, a direct interaction between DHLA and fibrinogen, the main protein in coagulation, is described. Binding constant for DHLA/fibrinogen complex is of moderate strength (104) and interaction probably occurs in D regions of fibrinogen, as shown by docking simulations. Fibrinogen stability remains the same with only marginal structural changes in its secondary structure favouring more ordered molecular organisation upon DHLA binding. Fibrinogen with bound DHLA forms fibrin with thicker fibers, as measured by coagulation assay and is protected from oxidation to certain extent. Obtained results support beneficial effects of DHLA on fibrinogen and consequently on coagulation process, suggesting that DHLA supplementation may be indicated for persons with an increased risk of developing thrombotic complications, particularly those whose fibrin is characterised by increased oxidative modification and formation of thinner and less porous fibers. Also, DHLA in complex with fibrinogen can be located at site of injury where it may exert antioxidant effects.

Biochemical and kinetic evaluation of the enzymatic toxins from two stinging scyphozoans Nemopilema nomurai and Cyanea nozakii.

Jellyfish envenomations are emerging as an important public health concern occurred worldwide. In China, the situation is getting worse with numerous people stung by jellyfish Nemopilema nomurai (N. nomurai) and Cyanea nozakii (C. nozakii) in the summer. However, the proteinaceous mixtures in nematocysts responsible for the symptoms of jellyfish stings were scarcely characterized and understood in view of enzymatic constituents and toxicity. In the present study, enzymatic properties of jellyfish N. nomurai and C. nozakii nematocyst venom were analyzed biochemically and kinetically. The current data revealed that N. nomurai and C. nozakii nematocyst venom exhibited various enzymatic activities, of which metalloproteinases activity and PLA2s-like activity were predominant. Moreover, the catalytic activities of metalloproteinases and PLA2s-like were dependent on different physiochemical conditions such as temperature, pH and divalent ions. Kinetic profiling revealed their catalytic behaviors fitted the Michaelis-Menten equation under specific conditions. Findings suggested jellyfish nematocyst venom possessed diverse enzymatic constituents, which may underlie the extensively characterized bioactivities of jellyfish venom and human envenomations. Hence, our study will contribute to understanding the enzymatic constituents and toxicity of jellyfish nematocyst venom and may afford potential therapeutic targets for developing drugs for jellyfish stings.

Effects on fibrinogen, fibrin, and blood coagulation of proteolytic extracts from fruits of Pseudananas macrodontes, Bromelia balansae, and B. hieronymi (Bromeliaceae) in comparison with bromelain.

Extracts rich in cysteine proteases obtained from fruits of Pseudananas macrodontes (Pm), Bromelia balansae (Bb), and B. hieronymi (Bh) have previously shown an anti-inflammatory effect on animal models. Given the close relationship between hemostasis and inflammation, it is attractive to investigate therapeutic agents capable of modulating both systems. The aim of this work was to study the effect of Pm, Bb, and Bh on fibrin(ogen) and blood coagulation compared with stem bromelain (Bro). Action on fibrinogen was electrophoretically and spectrophotometrically evaluated, fibrinolytic activity was measured both electrophoretically and by the fibrin plate assay, and the effect on blood coagulation was studied by conventional coagulation tests (PT and APPT). All extracts showed the same proteolytic preference for fibrinogen subunits, that is Aα > Bß, whereas γ was partially hydrolyzed by 100-fold concentration increase. Unlike Bro, cysteine proteases of Pm, Bb, and Bh increased absorbance at 540 nm of fibrinogen solution, suggesting thrombin-like activity, which was time-dependent and reached maximum values at lower concentration. All extracts showed the same proteolytic preference for fibrin subunits; however Pm, Bb, and Bh showed lower fibrinolytic activity than Bro at the assayed concentrations. Although Bb acted only as anticoagulant, Pm, Bh, and unexpectedly Bro showed dual action on blood coagulation: at low concentration showed procoagulant effect and at high concentration anticoagulant effect. Results reveal new plant species as potential sources of pharmacological agents for the treatment of a wide range of hemostatic disorders as well as to wound healing.

Antiplatelet activity of loureirin A by attenuating Akt phosphorylation: In vitro studies.

Loureirin A is a flavonoid extracted from Dragon׳s Blood that has been used to promote blood circulation and remove stasis in Chinese traditional medicine. However, the mechanisms of these effects are not fully understood. We explored the anti-platelet activity and underlying mechanism of loureirin A in vitro. Our results indicated that loureirin A negatively affected agonist-induced platelet aggregation such as collagen, collagen-related peptide (CRP), ADP and thrombin. Loureirin A inhibited collagen-induced platelet ATP secretion and thrombin-stimulated P-selectin expression in a dose-dependent manner. Platelet spreading on immobilized fibrinogen was significantly impaired in the presence of loureirin A. Immunoblotting analysis indicated that 100µM of loureirin A almost completely eliminated collagen-induced Akt phosphorylation at Ser473. Interestingly, a submaximal dose (50µM) of loureirin A had an additive inhibitory effect with the phosphoinositide 3-kinase (PI3K) inhibitor Ly294002 on collage-induced Akt phosphorylation in platelets. Taken together, loureirin A had an inhibitory effect on platelet activation, perhaps through an impairment of PI3K/Akt signaling.

Leonurus cardiaca L. herb--a derived extract and an ursolic acid as the factors affecting the adhesion capacity of Staphylococcus aureus in the context of infective endocarditis.

The objective was an assessment of the impact of Leonurus cardiaca L. extract (LCE) and ursolic acid (UA) on the adhesive properties of Staphylococus aureus NCTC 8325 strain, expressing virulence factors important in the pathogenesis of infective endocarditis. The adhesion and biofilm formation of bacteria cultured in the presence of subinhibitory concentrations of LCE or UA on the abiotic surface or covered with fibrinogen, fibronectin or collagen, were evaluated. Inhibitory effects of LCE and UA on staphylococcal adherence to both types of surface were demonstrated. This, in the case of UA, resulted in a significant reduction of biofilm formation.

Novel thrombolytic protease from edible and medicinal plant Aster yomena (Kitam.) Honda with anticoagulant activity: purification and partial characterization.

A thrombolytic protease named kitamase possessing anticoagulant property was purified from edible and medicinal plant Aster yomena (Kitam.) Honda. Kitamase showed a molecular weight of 50 kDa by SDS-PAGE and displayed a strong fibrin zymogram lysis band corresponding to the similar molecular mass. The enzyme was active at high temperatures (50°C). The fibrinolytic activity of kitamase was strongly inhibited by EDTA, EGTA, TPCK and PMSF, inhibited by Zn(2+). The Km and Vmax values for substrate S-2251 were determined as 4.31 mM and 23.81 mM/mg respectively. It dissolved fibrin clot directly and specifically cleaved the α, Aα and γ-γ chains of fibrin and fibrinogen. In addition, kitamase delayed the coagulation time and increased activated partial thromboplastin time and prothrombin time. Kitamase exerted a significant protective effect against collagen and epinephrine induced pulmonary thromboembolism in mice. These results suggest that kitamase may have the property of metallo-protease like enzyme, novel fibrino(geno)lytic enzyme and a potential to be a therapeutic agent for thrombosis.

Effect of Crocus sativus L. (saffron) on coagulation and anticoagulation systems in healthy volunteers.

Saffron showed some effects on blood coagulation and platelet aggregation in in vitro and in vivo studies. In a clinical trial with a limited number volunteers, saffron tablets influenced on bleeding time. In this study, the effect of saffron on plasma level of fibrinogen, factor VII (as coagulant agent), C and S protein (as anti-coagulant agent), PT and PTT in a larger sample size was evaluated. The study was a double-blind, placebo-controlled study consisting of 1 week treatment with 200 mg and 400 mg saffron tablets. Sixty healthy volunteers (age range 20-50 years) were selected for the study. The volunteers were divided into three groups of 20 each. Group 1 received placebo; Groups 2 and 3 received 200 mg and 400 mg saffron tablets, respectively, for 7 days (1 tablet per day). Before and after 7 days treatment and also 1 month after that, blood samples were taken. The plasma levels of fibrinogen, factor VII, C and S protein, PT and PTT were evaluated. Statistical analysis showed no difference between groups for any of evaluated factors. This study rejected any effect of saffron with dose of 200 and 400 mg for 1 week on coagulant and anticoagulant system.

Unusual clotting dynamics of plasma supplemented with iron(III).

Iron salts are used in the treatment of iron deficiency anemia. Diabetic patients are frequently anemic and treatment includes administration of iron. Anemic patients on hemodialysis are at an increased risk of thromboembolic coronary events associated with the formation of dense fibrin clots resistant to fibrinolysis. Moreover, in chronic kidney disease patients, high labile plasma iron levels associated with iron supplementation are involved in complications found in dialyzed patients such as myocardial infarction. The aim of the present study was to investigate whether iron treatment is involved in the formation of the fibrin clots. Clotting of citrated plasma supplemented with Fe(3+) was investigated by thromboelastometry and electron microscopy. The results revealed that iron modifies coagulation in a complex manner. FeCl(3) stock solution underwent gradual chemical modification during storage and altered the coagulation profile over 29 days, suggesting that Fe(3+) interacts with both proteins of the coagulation cascade as well as the hydrolytic Fe(3+) species. Iron extends clotting of plasma by interacting with proteins of the coagulation cascade. Fe(3+) and/or its hydrolytic species interact with fibrinogen and/or fibrin changing their morphology and properties. In general FeCl(3) weakens the fibrin clot while at the same time precipitating plasma proteins immediately after application. Fe(3+) or its derivatives induced the formation of insoluble coagulums in non-enzymatic reactions including albumin and transferrin. Iron plays a role in coagulation and can precipitate plasma proteins. The formation of coagulums resistant to lysis in non­enzymatic reactions can increase the risk of thrombosis, and extending clotting of plasma can prolong bleeding.

Generation of functional platelets from canine induced pluripotent stem cells.

Thrombocytopenia (TTP) is a blood disease common to canines and human beings. Currently, there is no valid therapy for this disease except blood transfusion. In this study, we report the generation of canine induced pluripotent stem cells (ciPSCs) from canine embryonic fibroblasts, and a novel protocol for creating mature megakaryocytes (MKs) and functional platelets from ciPSCs. The ciPSCs were generated using lentiviral vectors, and differentiated into MKs and platelets on OP9 stromal cells supplemented with growth factors. Our ciPSCs presented in a tightly domed shape and showed expression of a critical pluripotency marker, REX1, and normal karyotype. Additionally, ciPSCs differentiated into cells derived from three germ layers via the formation of an embryoid body. The MKs derived from ciPSCs had hyperploidy and transformed into proplatelets. The proplatelets released platelets early on that expressed specific MK and platelet marker CD41/61. Interestingly, these platelets, when activated with adenosine diphosphate or thrombin, bind to fibrinogen. Moreover, electron microscopy showed that the platelets had the same ultrastructure as peripheral platelets. Thus, we have demonstrated for the first time the generation of ciPSCs that are capable of differentiating into MKs and release functional platelets in vitro. Our system for differentiating ciPSCs into MKs and platelets promises a critical therapy for canine TTP and appears to be extensible in principle to resolve human TTP.

Aronia melanocarpa as a protector against nitration of fibrinogen.

Fibrinogen (Fg) also known as coagulation factor I represents about 4% of the total human plasma proteins. The main function of Fg is its involvement in last phase of blood coagulation cascade, when thrombin-induced conversion of dissolved plasma fibrinogen into an insoluble fibrin clot occurs. The reaction of fibrinogen with peroxynitrite causes both structural modifications and changes of the biological properties of this plasma glycoprotein. Recently, there is an increased interest in the screening of natural products present in fruits, vegetables and herbs for their possible antioxidative activities. Therefore, the aim of our study was to estimate the effect of extract from berries of Aronia melanocarpa against nitrative and oxidative damage induced by peroxynitrite. The extract from A. melanocarpa (0.5-50 µg/ml) added to Fg 10 min before peroxynitrite (100 µM) significantly inhibited both the formation of the high molecular weight protein aggregates and nitration of Fg molecule. The extract also abolished peroxynitrite-induced inhibition of fibrinogen polymerization (by 95% at 50 µg/ml). The obtained results indicate that natural extract from berries of A. melanocarpa has protective effects against peroxynitrite-induced nitrative damage of plasma fibrinogen, and therefore may contribute in the prevention of peroxynitrite-related cardiovascular or inflammatory diseases.

Anticoagulant activity of Moon jellyfish (Aurelia aurita) tentacle extract.

Moon jellyfish (Aurelia aurita) tentacle extract was studied for its anticoagulant activity in vitro. The Jellyfish Tentacle Extract (JFTE) showed very strong fibrinogenolytic activity by cleaving Aα and Bß chain of fibrinogen molecule. The fibrinogenolytic activity was found to be stronger than some snake venom derived anticoagulants. JFTE also completely liquefied fibrin clots in 24 h. JFTE was found to contain both high and low molecular weight proteins/peptides. The fibrinogenolysis appears to be caused by high molecular weight fractions of the extract. It has been also noted that PMSF significantly reduced fibrinogenolytic activity and heating totally abolished it. Autolytic degradation of the high molecular weight protein was also noted. Autolysis slowed down, but did not abolish the fibrinogenolytic activity of the extract.

Investigation of the mechanism(s) involved in decreasing increased fibrinogen activity in hyperglycemic conditions using L-lysine supplementation.

INTRODUCTION: Fibrinogen is a plasma glycoprotein that participates in the hemostasis system. Its malfunction has been reported as a consequence of diabetic complications. In this study, the inhibitory effect of L-Lysine (Lys) on the nonenzymatic glycation of fibrinogen was investigated in both in vitro and in vivo conditions. MATERIALS AND METHODS: Fibrinogen was incubated with glucose in the presence or absence of Lys. Then, its structure was studied by fluorescence spectroscopy, circular dichroism, and electrophoresis. The Clauss method was used to determine fibrinogen activity. In addition, one of the two groups of type 2 diabetic patients receiving ordinary treatment was additionally treated with Lys for 3 months. Fibrinogen activity and some other parameters were evaluated in their plasma. RESULTS: The results indicated increases in the activity of glycated fibrinogen in both of the in vivo and in vitro experiments. Advanced glycation end products were increased by time, as shown using fluorometry in both the plasma of the diabetic patients and the incubation medium of protein with glucose. The circular dichroism spectra showed some changes in the fibrinogen secondary and tertiary structures after glycation. The electrophoretic mobility of the glycated fibrinogen changed and the cross-link formation between the fibrinogen subunits due to glycation was observed. Lys inhibited all of the mentioned fibrinogen changes both in the in vitro experiments and after its administration to the diabetic patients. CONCLUSION: Lys, as an inhibitor of protein glycation, improved fibrinogen's structure and function, both in vitro and in vivo.

Aronia melanocarpa extract suppresses the biotoxicity of homocysteine and its metabolite on the hemostatic activity of fibrinogen and plasma.

OBJECTIVE: Aronia melanocarpa fruits (Rosaceae) are one of the richest plant sources of phenolic substances, and it has been shown to have various biological activities. Berries of A. melanocarpa (chokeberry) have been supposed to be beneficial for the prevention of cardiovascular events. In this study the influence of aronia extract on the clot formation (using human plasma and purified fibrinogen) and the fibrin lysis during the model of hyperhomocysteinemia was investigated. METHODS: Hyperhomocysteinemia was induced using a reduced form of Hcys (at final dose of 0.1mM) and the most reactive form of Hcys - its cyclic thioester, homocysteine thiolactone (HTL, 1 µM). The aim of our study in vitro was also to investigate the modifications of human plasma total proteins and the oxidative stress (by measuring the total antioxidant level - TAS) in plasma after incubation with Hcys, HTL and/or aronia extract. The biological properties of aronia extract were compared with the action of a well characterized antioxidative commercial polyphenol - resveratrol (3,4',5- trihydroxystilbene). RESULTS: The HTL, like its precursor, Hcys stimulated polymerization of fibrinogen. The results also demonstrated that Hcys (0.1mM) and HLT at lower doses than Hcys (1 µM) reduced the fibrin lysis in human plasma. Moreover, Hcys and HTL change the level of thiol and amino groups in plasma total proteins and induce the oxidative stress in plasma. Our results indicate that aronia extract reduced the biotoxicity action of Hcys and HTL on hemostatic properties of fibrinogen or plasma, suggesting its possible protective properties in hyperhomocysteinemia - induced cardiovascular diseases. Moreover, our results showed that the extract from berries of A. melanocarpa due to antioxidant action, significantly reduced the oxidative stress (measured by TAS) in plasma during the model of hyperhomocysteinemia. CONCLUSION: In the comparative studies, the extract from berries of A. melanocarpa and reseveratrol had similar protective properties. It gives hopes for development of diet supplements, which may be preventing thrombosis in pathological states where plasma procoagulant activity and oxidative stress are observed e.g. in hyperhomocysteinemia.

Histidine-rich glycoprotein binds fibrin(ogen) with high affinity and competes with thrombin for binding to the gamma'-chain.

Histidine-rich glycoprotein (HRG) is an abundant protein that binds fibrinogen and other plasma proteins in a Zn(2+)-dependent fashion but whose function is unclear. HRG has antimicrobial activity, and its incorporation into fibrin clots facilitates bacterial entrapment and killing and promotes inflammation. Although these findings suggest that HRG contributes to innate immunity and inflammation, little is known about the HRG-fibrin(ogen) interaction. By immunoassay, HRG-fibrinogen complexes were detected in Zn(2+)-supplemented human plasma, a finding consistent with a high affinity interaction. Surface plasmon resonance determinations support this concept and show that in the presence of Zn(2+), HRG binds the predominant γ(A)/γ(A)-fibrinogen and the γ-chain elongated isoform, γ(A)/γ'-fibrinogen, with K(d) values of 9 nm. Likewise, (125)I-labeled HRG binds γ(A)/γ(A)- or γ(A)/γ'-fibrin clots with similar K(d) values when Zn(2+) is present. There are multiple HRG binding sites on fibrin(ogen) because HRG binds immobilized fibrinogen fragment D or E and γ'-peptide, an analog of the COOH terminus of the γ'-chain that mediates the high affinity interaction of thrombin with γ(A)/γ'-fibrin. Thrombin competes with HRG for γ'-peptide binding and displaces (125)I-HRG from γ(A)/γ'-fibrin clots and vice versa. Taken together, these data suggest that (a) HRG circulates in complex with fibrinogen and that the complex persists upon fibrin formation, and (b) by competing with thrombin for γ(A)/γ'-fibrin binding, HRG may modulate coagulation. Therefore, the HRG-fibrin interaction may provide a novel link between coagulation, innate immunity, and inflammation.

Sulfotanshinone Sodium Injection could decrease fibrinogen level and improve clinical outcomes in patients with unstable angina pectoris.

We randomly divided 100 unstable angina pectoris (UAP) patients into two groups: the trial group received Sulfotanshinone Sodium Injection (SSI) 60 mg combined with a loading dose of 300 mg aspirin and a maintenance dose of 100 mg of aspirin plus baseline therapy, and the control group received the same doses of aspirin and baseline therapy. 94 patients completed treatment. After 4 weeks' medication, the severity of angina pectoris improved in both groups, with a significant improvement in total effective rate in the trial group but no difference in the total effective rate of improvement seen on ECG. Compared with baseline level, FIB level after treatment decreased significantly in both groups but to a greater extent in the trial group. Similar changes in DD levels were observed in both groups. With a background of aspirin and baseline therapy, SSI can significantly attenuate angina pectoris attacks in patients with UAP which may be associated with the decreased level of FIB.

Surface plasmon resonance spectroscopy study of interfacial binding of thrombin to antithrombin DNA aptamers.

We have applied surface plasmon resonance (SPR) spectroscopy, in combination with one-step direct binding, competition, and sandwiched assay schemes, to study thrombin binding to its DNA aptamers, with the aim to further the understanding of their interfacial binding characteristics. Using a 15-mer aptamer that binds thrombin primarily at the fibrinogen-recognition exosite as a model, we have demonstrated that introducing a DNA spacer in the aptamer enhances thrombin-binding capacity and stability, as similarly reported for hydrocarbon linkers. The bindings are aptamer surface coverage and salt concentration dependent. When free aptamers or DNA sequences complementary to the immobilized aptamer are applied after the formation of thrombin/aptamer complexes, bound thrombin is displaced to a certain extent, depending on the stability of the complexes formed under different conditions. When the 29-mer aptamer (specific to thrombin's heparin-binding exosite) is immobilized on the surface, its affinity to thrombin appears to be lower than the immobilized 15-mer aptamer, although the 29-mer aptamer is known to have a higher affinity in the solution phase. These findings underline the importance of aptamers' ability to fold into intermolecular structures and their accessibility for target capture. Using a sandwiched assay scheme followed by an additional signaling step involving biotin-streptavidin chemistry, we have observed the simultaneous binding of the 15- and 29-mer aptamers to thrombin protein at different exosites and have found that one aptamer depletes thrombin's affinity to the other when they bind together. We believe that these findings are invaluable for developing DNA aptamer-based biochips and biosensors.