Recombinant thrombomodulin and recombinant antithrombin attenuate pulmonary endothelial glycocalyx degradation and neutrophil extracellular trap formation in ventilator-induced lung injury in the context of endotoxemia.

BACKGROUND: Vascular endothelial damage is involved in the development and exacerbation of ventilator-induced lung injury (VILI). Pulmonary endothelial glycocalyx and neutrophil extracellular traps (NETs) are endothelial protective and damaging factors, respectively; however, their dynamics in VILI and the effects of recombinant thrombomodulin and antithrombin on these dynamics remain unclear. We hypothesized that glycocalyx degradation and NETs are induced by VILI and suppressed by recombinant thrombomodulin, recombinant antithrombin, or their combination. METHODS: VILI was induced in male C57BL/6J mice by intraperitoneal lipopolysaccharide injection (20 mg/kg) and high tidal volume ventilation (20 mL/kg). In the intervention groups, recombinant thrombomodulin, recombinant antithrombin, or their combination was administered at the start of mechanical ventilation. Glycocalyx degradation was quantified by measuring serum syndecan-1, fluorescence-labeled lectin intensity, and glycocalyx-occupied area in the pulmonary vascular lumen. Double-stranded DNA in the bronchoalveolar fluid and fluorescent areas of citrullinated histone H3 and myeloperoxidase were quantified as NET formation. RESULTS: Serum syndecan-1 increased, and lectin fluorescence intensity decreased in VILI. Electron microscopy revealed decreases in glycocalyx-occupied areas within pulmonary microvessels in VILI. Double-stranded DNA levels in the bronchoalveolar lavage fluid and the fluorescent area of citrullinated histone H3 and myeloperoxidase in lung tissues increased in VILI. Recombinant thrombomodulin, recombinant antithrombin, and their combination reduced glycocalyx injury and NET marker levels. There was little difference in glycocalyx injury and NET makers between the intervention groups. CONCLUSION: VILI induced glycocalyx degradation and NET formation. Recombinant thrombomodulin and recombinant antithrombin attenuated glycocalyx degradation and NETs in our VILI model. The effect of their combination did not differ from that of either drug alone. Recombinant thrombomodulin and antithrombin have the potential to be therapeutic agents for biotrauma in VILI.

Application Value and Safety Analysis of Warfarin, Rivaroxaban, and Dabigatran Ester in Elderly Patients With Atrial Fibrillation.

BACKGROUND: This study aimed to evaluate the application value and safety of Warfarin, Rivaroxaban, and Dabigatran in elderly patients with atrial fibrillation. METHODS: A total of 180 elderly patients with atrial fibrillation admitted to our hospital were retrospectively analyzed. According to their anticoagulant treatment regimen, patients were divided into three groups: Warfarin (57 cases), Rivaroxaban (61 cases), and Dabigatran (62 cases). General demographic information was collected, and coagulation function indicators-including fibrinogen (FIB), thrombin time (PT), activated partial thrombin time (APTT), and D-dimer (D-D)-as well as liver function indexes-including total bilirubin (TbiL), alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine transferase (ALT)-were compared before and after 4 weeks of treatment. RESULTS: There were no significant differences in demographic characteristics such as gender, age, body mass index, or disease course among the three groups. The total effective rate in the Warfarin group (84.21%) was significantly lower than in the Rivaroxaban (98.36%) and Dabigatran (96.77%) groups (p < 0.05). However, there was no significant difference in the total effective rate between the Rivaroxaban and Dabigatran groups (p > 0.05). Additionally, no significant differences were found in the effects of the three drugs on coagulation function, liver function, or the incidence of bleeding (p = 0.052). CONCLUSION: Warfarin, Rivaroxaban, and Dabigatran can effectively prevent thrombosis in elderly patients with atrial fibrillation, with Rivaroxaban and Dabigatran showing superior effectiveness. All three drugs demonstrated similar low rates of bleeding events and had no significant impact on coagulation and liver function.

Thrombolysis After Dabigatran Reversal for Acute Ischemic Stroke: A National Registry-Based Study and Meta-Analysis.

BACKGROUND AND OBJECTIVES: Limited data exist on the safety of IV thrombolysis (IVT) for acute ischemic stroke (AIS) after dabigatran reversal with idarucizumab. We sought to evaluate the safety and efficacy of idarucizumab pretreatment in patients with AIS receiving IVT. METHODS: A national registry-based study evaluated the safety and efficacy of IVT in this specific subgroup. We also conducted a systematic review and meta-analysis of cohort studies and case series, aiming to document the pooled rates of (1) symptomatic intracranial hemorrhage (sICH), (2) any intracranial hemorrhage, (3) 3-month mortality, and (4) the proportion of excellent (modified Rankin Scale [mRS] scores 0-1) and (5) good (mRS scores 0-2) functional outcome at 3 months among patients with AIS, who received IVT after dabigatran reversal with idarucizumab. Moreover, we sought to compare these outcomes between IVT-treated patients after dabigatran reversal with idarucizumab and IVT-treated patients without dabigatran pretreatment. RESULTS: Thirteen cohorts including our nation-wide registry-based cohort and 1 case series comprising 553 patients with AIS (mean age: 75 years; male sex: 65%; median baseline NIH Stroke Scale score: 11 points) receiving idarucizumab before IVT were included in this meta-analysis. The pooled rate of sICH after IVT after idarucizumab administration was 4% (95% CI 1-9; I2 = 26%), while the pooled rates of any intracranial hemorrhage and 3-month mortality were 10% (95% CI 5-16; I2 = 24%) and 18% (95% CI 10-27; I2 = 0%), respectively. The pooled rates of excellent and good functional outcomes at 3 months were 56% (95% CI 27-83; I2 = 69%) and 70% (95% CI 57-81; I2 = 40%), respectively. The risk of sICH (risk ratio [RR] 1.86; 95% CI 0.91-3.80; I2 = 0%), any intracranial hemorrhage (RR 1.76; 95% CI 0.99-3.11; I2 = 8%), and 3-month mortality (RR 1.50; 95% CI 0.91-2.48; I2 = 0%) did not differ between patients with AIS receiving IVT with and without idarucizumab. Moreover, idarucizumab administration was associated with higher likelihood of achieving a 3-month good functional outcome (RR 1.35; 95% CI 1.11-1.65; I2 = 27%). DISCUSSION: IVT for AIS after dabigatran reversal with idarucizumab seems to be safe and effective in observational studies with limited number of patients. Randomized-controlled clinical trials are warranted to provide robust evidence on the safety and efficacy of IVT in this specific AIS subgroup.

Comparison of Three Different Disseminated Intravascular Coagulation (DIC) Criteria and Diagnostic and Prognostic Value of Antithrombin Investigation in Patients with Confirmed Sepsis-Induced Coagulopathy (SIC).

A new scoring system termed sepsis-induced coagulopathy (SIC) has been proposed to diagnose early sepsis-induced disseminated intravascular coagulation (DIC). This study performed DIC-related analyses in patients with confirmed SIC. Data from the intensive care unit (ICU) departments of the three hospitals between 2020 and 2022 were retrospectively analyzed. Finally, 125 patients with confirmed SIC were enrolled in the study. The diagnostic value of three widely used DIC criteria was assessed in patients with newly diagnosed SIC. In addition, the diagnostic and prognostic value of antithrombin (AT) was analyzed in patients with SIC. The Japanese Association for Acute Medicine DIC criteria (JAAM) exhibited the highest DIC diagnostic rate, while the mortality risk of SIC patients demonstrated a proportional increase with higher International Society on Thrombosis and Haemostasis (ISTH) and Chinese DIC scoring system (CDSS) scores. Low AT activity (<70%) in septic patients upon SIC diagnosis predicted a very high 28-day mortality rate, almost twice as high as in the normal AT activity (≥70%) group. A decreasing tendency in AT activity after clinical interventions was correlated with increased mortality. The area under the ROC curve (AU-ROC) of AT in DIC diagnosis was statistically significant when CDSS and ISTH were used as diagnostic criteria, but not JAAM. Each of the three DIC diagnostic criteria showed diagnostic and prognostic advantages for SIC. AT could be an independent prognostic indicator for SIC but demonstrated a relatively limited DIC diagnostic value. Adding AT to the SIC scoring system may increase its prognostic power.

Recommendations on Monitoring and Replacement of Antithrombin, Fibrinogen, and Von Willebrand Factor in Pediatric Patients on Extracorporeal Membrane Oxygenation: The Pediatric Extracorporeal Membrane Oxygenation Anticoagulation CollaborativE Consensus Conference.

OBJECTIVES: To derive systematic review informed, modified Delphi consensus regarding monitoring and replacement of specific coagulation factors during pediatric extracorporeal membrane oxygenation (ECMO) support for the Pediatric ECMO Anticoagulation CollaborativE. DATA SOURCES: A structured literature search was performed using PubMed, Embase, and Cochrane Library (CENTRAL) databases from January 1988 to May 2020, with an update in May 2021. STUDY SELECTION: Included studies assessed monitoring and replacement of antithrombin, fibrinogen, and von Willebrand factor in pediatric ECMO support. DATA EXTRACTION: Two authors reviewed all citations independently, with conflicts resolved by a third reviewer if required. Twenty-nine references were used for data extraction and informed recommendations. Evidence tables were constructed using a standardized data extraction form. DATA SYNTHESIS: Risk of bias was assessed using the Quality in Prognosis Studies tool. The evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation system. A panel of 48 experts met over 2 years to develop evidence-based recommendations and, when evidence was lacking, expert-based consensus statements. A web-based modified Delphi process was used to build consensus via the Research And Development/University of California Appropriateness Method. Consensus was defined as greater than 80% agreement. We developed one weak recommendation and four expert consensus statements. CONCLUSIONS: There is insufficient evidence to formulate recommendations on monitoring and replacement of antithrombin, fibrinogen, and von Willebrand factor in pediatric patients on ECMO. Optimal monitoring and parameters for replacement of key hemostasis parameters is largely unknown.

Direct factor Xa inhibitors and the risk of cancer and cancer mortality: A Danish population-based cohort study.

BACKGROUND: Preclinical animal studies have suggested that myeloid cell-synthesized coagulation factor X dampens antitumor immunity and that rivaroxaban, a direct factor Xa inhibitor, can be used to promote tumor immunity. This study was aimed at assessing whether patients with atrial fibrillation taking direct factor Xa inhibitors have lower risk of cancer and cancer-related mortality than patients taking the direct thrombin inhibitor dabigatran. METHODS AND FINDINGS: This nationwide population-based cohort study in Denmark included adult patients with atrial fibrillation and without a history of cancer, who started taking a factor Xa inhibitor or dabigatran between 2011 and 2015. Data on medical history, outcomes, and drug use were acquired through Danish healthcare registries. The primary outcome was any cancer. Secondary outcomes were cancer-related mortality and all-cause mortality. Outcome events were assessed during 5 years of follow-up in an intention-to-treat analysis. The propensity score-based inverse probability of treatment weighting was used to compute cumulative incidence and subdistribution hazard ratios (SHRs) and corresponding 95% confidence intervals (CIs), with death as a competing event. Propensity scores were estimated using logistic regression and including in the model sex, age group at index date, comorbidities, and use of comedications. A total of 11,742 patients with atrial fibrillation starting a factor Xa inhibitor and 11,970 patients starting dabigatran were included. Mean age was 75.2 years (standard deviation [SD] 11.2) in the factor Xa cohort and 71.7 years (SD 11.1) in the dabigatran cohort. On the basis of the propensity score-weighted models, after 5 years of follow-up, no substantial difference in the cumulative incidence of cancer was observed between the factor Xa inhibitor (2,157/23,711; 9.11%, 95% CI [8.61%,9.63%]) and dabigatran (2,294/23,715; 9.68%, 95% CI [9.14%,10.25%]) groups (SHR 0.94, 95% CI [0.89,1.00], P value 0.0357). We observed no difference in cancer-related mortality (factor Xa inhibitors cohort 1,028/23,711; 4.33%, 95% CI [4.02%,4.68%]. Dabigatran cohort 1,001/23,715; 4.22%, 95% CI [3.83%,4.66%]; SHR 1.03, 95% CI [0.94,1.12]), but all-cause mortality was higher in the factor Xa inhibitor cohort (factor Xa inhibitors cohort 7,416/23,711; 31.31%, 95% CI [30.37%,32.29%]. Dabigatran cohort 6,531/23,715; 27.56%, 95% CI [26.69%,28.45%]; HR 1.17, 95% CI [1.13,1.21]). The main limitations of the study were the possibility of residual confounding and the short follow-up period. CONCLUSIONS: In this population based cohort study, factor Xa inhibitor use was not associated with an overall lower incidence of cancer or cancer-related mortality when compared to dabigatran. We did observe an increase in all-cause mortality in the factor Xa inhibitor cohort.

The impact of heparin and direct thrombin inhibitors on cell-penetrating polymer siRNA transfection.

Gene therapy using siRNA has become a promising strategy to achieve targeted gene knockdown for treatment of cardiovascular pathologies. However, efficient siRNA transfection often relies on cationic delivery vectors such as synthetic cell-penetrating polymers which are susceptible to interference by negatively charged molecules. Anticoagulants such as heparin, which is negatively charged and widely used in cardiovascular applications, may pose a significant barrier to effective siRNA delivery. We therefore conducted in vitro studies utilizing human smooth muscle and endothelial cells transfected with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and ß2-microglobulin (B2M) siRNA in the presence of heparin, argatroban, and bivalirudin in order to determine which anticoagulant therapy is most compatible for siRNA delivery. We observed that while heparin, at clinical doses, decreases the efficiency of siRNA targeted mRNA knockdown, mRNA knockdown is not inhibited in the presence of either argatroban or bivalirudin. Our data suggests that heparin should be avoided during siRNA therapy with cationic transfection agents, and argatroban and bivalirudin should be used in its stead.

Comparison of warfarin, rivaroxaban, and dabigatran for effectiveness and safety in atrial fibrillation patients with different CHA2DS2-VASc scores: a retrospective cohort study.

BACKGROUND: This retrospective cohort study aims to compare the effectiveness and safety of warfarin, rivaroxaban, and dabigatran in atrial fibrillation (AF) patients with different CHA2DS2-VASc scores in northern China. METHODS: A retrospective cohort study was performed to evaluate anticoagulation in AF patients at the second affiliated hospital of Harbin Medical University from September 2018 to August 2019. Patients included in this study (n = 806) received warfarin (n = 300), or rivaroxaban (n = 203), or dabigatran (n = 303). Baseline characteristics and follow-up data including adherence, bleeding events and ischemic stroke (IS) events were collected. RESULTS: Patients receiving rivaroxaban (73.9%) or dabigatran (73.6%) showed better adherence than those receiving warfarin (56.7%). Compared with warfarin-treated patients, dabigatran-treated patients had lower incidence of bleeding events (10.9% vs 19.3%, χ2 = 8.385, P = 0.004) and rivaroxaban-treated patients had lower incidence of major adverse cardiovascular events (7.4% vs 13.7%, χ2 = 4.822, P = 0.028). We classified patients into three groups based on CHA2DS2-VASc score (0-1, 2-3, ≥ 4). In dabigatran intervention, incidence of bleeding events was higher in patients with score 0-1 (20.0%) than those with score 2-3 (7.9%, χ2 = 5.772, P = 0.016) or score ≥ 4 (8.6%, χ2 = 4.682, P = 0.030). Patients with score 0-1 in warfarin or rivaroxaban therapy had a similar but not significant increase of bleeding compared with patients with score 2-3 or score ≥ 4, respectively. During the follow-up, 33 of 806 patients experienced IS and more than half (19, 57.6%) were patients with score ≥ 4. Comparing patients with score 0-1 and 2-3, the latter had an significant reduction of IS in patients prescribed warfarin and non-significant reduction in rivaroxaban and dabigatran therapy. CONCLUSION: Compared with warfarin therapy, patients with different CHA2DS2-VASc scores receiving either rivaroxaban or dabigatran were associated with higher persistence. AF patients with score ≥ 4 were more likely to experience IS events while hemorrhagic tendency preferred patients with low score 0-1.

Antithrombin testing and treatment in pregnancy: Their real-world relationship to clinical outcomes.

BACKGROUND: Antithrombin (AT) deficiency is a severe thrombophilia associated with increased rates of maternal morbidity, mortality, and greater healthcare resource utilization during pregnancy and postpartum. METHODS: Two large U.S. healthcare databases were queried for women aged 15-44 with delivery-related encounters: Cerner Real-World Data (CRWD, 01/01/2000-12/31/2021) and Premier Healthcare Database (PHD, 01/01/2016-01/01/2019). Individuals receiving cardiopulmonary bypass were excluded. Three cohorts were created: 1) Individuals who had AT levels tested any time between 9-months pre- through 3-months post-delivery (CRWD Test Cohort); 2) individuals prescribed AT concentrate (ATc) within 1-year pre- or 1-year post-delivery in CRWD (CRWD Medication Cohort); and 3) the same criteria as 2) applied to PHD (PHD Medication Cohort). RESULTS: There were 5411 individuals in the CRWD Test Cohort, 13 in the CRWD Medication Cohort and 38 in the PHD Medication Cohort. Demographic and baseline clinical characteristics were similar across cohorts. AT level testing occurred pre-delivery in 47.9 % of the CRWD Test Cohort and 23.1 % of the CRWD Medication Cohort. ATc was administered during the delivery hospitalization to 0.1 %, 23.1 % and 50.0 % of the CRWD Test, CRWD Medication, and PHD Medication Cohorts, respectively. Across cohorts, 5.4-7.9 % of individuals experienced thrombosis during the delivery-related encounter. Mean (SD) total costs for delivery through 1-year post-delivery were $190,894 ($276,893) with $123,763 ($177,122) of total costs related to abnormal coagulation. CONCLUSION: Opportunities exist to enhance the care of pregnant individuals with low AT levels throughout pregnancy, aiming for optimal maternal outcomes.

Clot-Targeted Nanogels for Dual-Delivery of AntithrombinIII and Tissue Plasminogen Activator to Mitigate Disseminated Intravascular Coagulation Complications.

Disseminated intravascular coagulation (DIC) is a pathologic state that follows systemic injury and other diseases. Often a complication of sepsis or trauma, DIC causes coagulopathy associated with paradoxical thrombosis and hemorrhage. DIC upregulates the thrombotic pathways while simultaneously downregulating the fibrinolytic pathways that cause excessive fibrin deposition, microcirculatory thrombosis, multiorgan dysfunction, and consumptive coagulopathy with excessive bleeding. Given these opposing disease phenotypes, DIC management is challenging and includes treating the underlying disease and managing the coagulopathy. Currently, no therapies are approved for DIC. We have developed clot-targeted therapeutics that inhibit clot polymerization and activate clot fibrinolysis to manage DIC. We hypothesize that delivering both an anticoagulant and a fibrinolytic agent directly to clots will inhibit active clot polymerization while also breaking up pre-existing clots; therefore, reversing consumptive coagulopathy and restoring hemostatic balance. To test this hypothesis, we single- and dual-loaded fibrin-specific nanogels (FSNs) with antithrombinIII (ATIII) and/or tissue plasminogen activator (tPA) and evaluated their clot preventing and clot lysing abilities in vitro and in a rodent model of DIC. In vivo, single-loaded ATIII-FSNs decreased fibrin deposits in DIC organs and reduced blood loss when DIC rodents were injured. We also observed that the addition of tPA in dual-loaded ATIII-tPA-FSNs intensified the antithrombotic and fibrinolytic mechanisms, which proved advantageous for clot lysis and restoring platelet counts. However, the addition of tPA may have hindered wound healing capabilities when an injury was introduced. Our data supports the benefits of delivering both anticoagulants and fibrinolytic agents directly to clots to reduce the fibrin load and restore hemostatic balance in DIC.

Discovery and Characterization of Panaxatriol as a Novel Thrombin Inhibitor from Panax notoginseng Using a Combination of Computational and Experimental Approaches.

Thrombin is a crucial enzyme in the coagulation cascade, and inhibitors of thrombin have been extensively studied as potential antithrombotic agents. The objective of this study was to identify natural inhibitors of thrombin from Panax notoginseng and evaluate their biological activity in vitro and binding characteristics. A combined approach involving molecular docking, thrombin inhibition assays, surface plasmon resonance, and molecular dynamics simulation was utilized to identify natural thrombin inhibitors. The results demonstrated that panaxatriol directly inhibits thrombin, with an IC50 of 10.3 µM. Binding studies using surface plasmon resonance revealed that panaxatriol interacts with thrombin, with a KD value of 7.8 µM. Molecular dynamics analysis indicated that the thrombin-panaxatriol system reached equilibrium rapidly with minimal fluctuations, and the calculated binding free energy was - 23.8 kcal/mol. The interaction between panaxatriol and thrombin involves the amino acid residues Glu146, Glu192, Gly216, Gly219, Tyr60A, and Trp60D. This interaction provides a mechanistic basis for further optimizing panaxatriol as a thrombin inhibitor. Our study has shown that panaxatriol serves as a direct thrombin inhibitor, laying the groundwork for further research and development of novel thrombin inhibitors.

Molecular Mechanisms of the Impaired Heparin Pentasaccharide Interactions in 10 Antithrombin Heparin Binding Site Mutants Revealed by Enhanced Sampling Molecular Dynamics.

Antithrombin (AT) is a critical regulator of the coagulation cascade by inhibiting multiple coagulation factors including thrombin and FXa. Binding of heparinoids to this serpin enhances the inhibition considerably. Mutations located in the heparin binding site of AT result in thrombophilia in affected individuals. Our aim was to study 10 antithrombin mutations known to affect their heparin binding in a heparin pentasaccharide bound state using two molecular dynamics (MD) based methods providing enhanced sampling, GaMD and LiGaMD2. The latter provides an additional boost to the ligand and the most important binding site residues. From our GaMD simulations we were able to identify four variants (three affecting amino acid Arg47 and one affecting Lys114) that have a particularly large effect on binding. The additional acceleration provided by LiGaMD2 allowed us to study the consequences of several other mutants including those affecting Arg13 and Arg129. We were able to identify several conformational types by cluster analysis. Analysis of the simulation trajectories revealed the causes of the impaired pentasaccharide binding including pentasaccharide subunit conformational changes and altered allosteric pathways in the AT protein. Our results provide insights into the effects of AT mutations interfering with heparin binding at an atomic level and can facilitate the design or interpretation of in vitro experiments.

Therapeutic Potentials of Medicinal Leech in Chinese Medicine.

The use of medicinal leeches in clinical therapy has been employed for a long time, as it was originally recognized for exerting antithrombin effects. These effects were due to the ability of the leech to continuously suck blood while attached to human skin. According to Chinese Pharmacopoei, leeches used in traditional Chinese medicine mainly consist of Whitmania pigra Whitman, Hirudo nipponia Whitman, and Whitmania acranulata, but the latter two species are relatively scarce. The main constituents of leeches are protein and peptide macromolecules. They can be categorized into two categories based on their pharmacological effects. One group consists of active ingredients that directly target the coagulation system, such as hirudin, heparin, and histamine, which are widely known. The other group comprises protease inhibitor components like Decorsin and Hementin. Among these, hirudin secreted by the salivary glands of the leech is the most potent thrombin inhibitor and served as the sole remedy for preventing blood clotting until the discovery of heparin. Additionally, leeches play a significant role in various traditional Chinese medicine formulations. In recent decades, medicinal leeches have been applied in fields including anti-inflammatory treatment, cardiovascular disease management, antitumor treatment, and many other medical conditions. In this review, we present a comprehensive overview of the historical journey and medicinal applications of leeches in various medical conditions, emphasizing their pharmaceutical significance within traditional Chinese medicine. This review offers valuable insights for exploring additional therapeutic opportunities involving the use of leeches in various diseases and elucidating their underlying mechanisms for future research.

Distinct antithrombin activation modes for fondaparinux and natural heparins detected using millisecond hydrogen deuterium exchange and collision induced unfolding.

Low molecular weight heparin and synthetic mimetics such as fondaparinux show different binding kinetics, protease specificity, and clinical effects. A combination of allosteric and template-mediated bridging mechanisms have been proposed to explain the differences in rate acceleration and specificity. The difficulty in working with heterogeneous heparin species has rendered a crystallographic interpretation of the differences in antithrombin activation between mimetics and natural heparin inaccessible. In this study, we examine the allosteric changes in antithrombin caused by binding fondaparinux, enoxaparin and depolymerized natural heparins using millisecond hydrogen deuterium exchange mass spectrometry (TRESI-HDX MS) and relate these conformational changes to complex stability in the gas phase using collision induced unfolding (CIU). This exploration reveals that in addition to the dynamic changes caused by fondaparinux, long chain heparins reduce structural flexibility proximal to Arg393, the cleavable residue in the reactive centre loop of the protein. These local changes in protein dynamics are associated with an increase in overall complex stability that increases with heparin chain length. Ultimately, these results shed light on the molecular mechanisms underlying differences in activity and specificity between heparin mimetics and natural heparins.

Ramadan intermittent fasting is associated with improved anticoagulant activity among healthy people: a case-control study.

Data on the pathophysiological mechanisms of hemostatic alterations in the thrombotic events that occur during Ramadan intermittent fasting (RIF), particularly in the natural coagulation inhibitors, are very limited. Thus, our objective was to evaluate the effect of RIF on the natural anticoagulants level, antithrombin, protein C, and total and free protein S (PS) in healthy participants. Participants were divided into two groups. Group I consisted of 29 healthy fasting participants whose blood samples were taken after 20 days of fasting. Group II included 40 healthy non-fasting participants whose blood samples were taken 2-4 weeks before the month of Ramadan. Coagulation screening tests including prothrombin time (PT), activated partial thromboplastin time (APTT) and plasma fibrinogen level, natural anticoagulants; antithrombin, protein C, free and total PS and C4 binding protein (C4BP) levels were evaluated in the two groups. High levels of total and free PS without change in antithrombin, protein C, and C4BP levels were noted in the fasting group as compared with non-fasting ones (p < 0.05). PT and APTT showed no difference between the two groups. However, the fibrinogen level was higher in the fasting group. In conclusion, RIF was found to be associated with improved anticoagulant activity in healthy participants, which may provide temporal physiological protection against the development of thrombosis in healthy fasting people.

Unveiling dynamics of nitrogen content and selected nitrogen heterocycles in thrombin inhibitors: a ceteris paribus approach.

BACKGROUND: Despite the progress in comprehending molecular design principles and biochemical processes associated with thrombin inhibition, there is a crucial need to optimize efforts and curtail the recurrence of synthesis-testing cycles. Nitrogen and N-heterocycles are key features of many anti-thrombin drugs. Hence, a pragmatic analysis of nitrogen and N-heterocycles in thrombin inhibitors is important throughout the drug discovery pipeline. In the present work, the authors present an analysis with a specific focus on understanding the occurrence and distribution of nitrogen and selected N-heterocycles in the realm of thrombin inhibitors. RESEARCH DESIGN AND METHODS: A dataset comprising 4359 thrombin inhibitors is used to scrutinize various categories of nitrogen atoms such as ring, non-ring, aromatic, and non-aromatic. In addition, selected aromatic and aliphatic N-heterocycles have been analyzed. RESULTS: The analysis indicates that ~62% of thrombin inhibitors possess five or fewer nitrogen atoms. Substituted N-heterocycles have a high occurrence, like pyrrolidine (23.24%), pyridine (20.56%), piperidine (16.10%), thiazole (9.61%), imidazole (7.36%), etc. in thrombin inhibitors. CONCLUSIONS: The majority of active thrombin inhibitors contain nitrogen atoms close to 5 and a combination of N-heterocycles like pyrrolidine, pyridine, piperidine, etc. This analysis provides crucial insights to optimize the transformation of lead compounds into potential anti-thrombin inhibitors.

A functional RNA-origami as direct thrombin inhibitor with fast-acting and specific single-molecule reversal agents in vivo model.

Injectable anticoagulants are widely used in medical procedures to prevent unwanted blood clotting. However, many lack safe, effective reversal agents. Here, we present new data on a previously described RNA origami-based, direct thrombin inhibitor (HEX01). We describe a new, fast-acting, specific, single-molecule reversal agent (antidote) and present in vivo data for the first time, including efficacy, reversibility, preliminary safety, and initial biodistribution studies. HEX01 contains multiple thrombin-binding aptamers appended on an RNA origami. It exhibits excellent anticoagulation activity in vitro and in vivo. The new single-molecule, DNA antidote (HEX02) reverses anticoagulation activity of HEX01 in human plasma within 30 s in vitro and functions effectively in a murine liver laceration model. Biodistribution studies of HEX01 in whole mice using ex vivo imaging show accumulation mainly in the liver over 24 h and with 10-fold lower concentrations in the kidneys. Additionally, we show that the HEX01/HEX02 system is non-cytotoxic to epithelial cell lines and non-hemolytic in vitro. Furthermore, we found no serum cytokine response to HEX01/HEX02 in a murine model. HEX01 and HEX02 represent a safe and effective coagulation control system with a fast-acting, specific reversal agent showing promise for potential drug development.

Differential Solvent DEEP-STD NMR and MD Simulations Enable the Determinants of the Molecular Recognition of Heparin Oligosaccharides by Antithrombin to Be Disentangled.

The interaction of heparin with antithrombin (AT) involves a specific sequence corresponding to the pentasaccharide GlcNAc/NS6S-GlcA-GlcNS3S6S-IdoA2S-GlcNS6S (AGA*IA). Recent studies have revealed that two AGA*IA-containing hexasaccharides, which differ in the sulfation degree of the iduronic acid unit, exhibit similar binding to AT, albeit with different affinities. However, the lack of experimental data concerning the molecular contacts between these ligands and the amino acids within the protein-binding site prevents a detailed description of the complexes. Differential epitope mapping (DEEP)-STD NMR, in combination with MD simulations, enables the experimental observation and comparison of two heparin pentasaccharides interacting with AT, revealing slightly different bound orientations and distinct affinities of both glycans for AT. We demonstrate the effectiveness of the differential solvent DEEP-STD NMR approach in determining the presence of polar residues in the recognition sites of glycosaminoglycan-binding proteins.