The Role of Recombinant Hirudins in the Management of Thrombotic Disorders

Recombinant hirudin and PAR-1 regulate macrophage polarisation status in diffuse large B-cell lymphoma

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is a malignant tumour. Although some standard therapies have been established to improve the cure rate, they remain ineffective for specific individuals. Therefore, it is meaningful to find more novel therapeutic approaches. Macrophage polarisation is extensively involved in the process of tumour development. Recombinant hirudin (rH) affects macrophages and has been researched frequently in clinical trials lately. Our article validated the regulatory role of rH in macrophage polarisation and the mechanism of PAR-1 by collecting clinical samples and subsequently establishing a cellular model to provide a scientifically supported perspective for discovering new therapeutic approaches.

METHOD

We assessed the expression of macrophage polarisation markers, cytokines and PAR-1 in clinical samples. We established a cell model by co-culture with THP-1 and OCI-Ly10 cell. We determined the degree of cell polarisation and expression of validation cytokines by flow cytometry, ELISA, and RT-qPCR to confirm the success of the cell model. Subsequently, different doses of rH were added to discover the function of rH on cell polarisation. We confirmed the mechanism of PAR-1 in macrophage polarisation by transfecting si-PAR-1 and pcDNA3.1-PAR-1.

RESULTS

We found higher expression of M2 macrophage markers (CD163 + CMAF+) and PAR-1 in 32 DLBCL samples. After inducing monocyte differentiation into M0 macrophages and co-culturing with OCI-Ly10 lymphoma cells, we found a trend of these expressions in the cell model consistent with the clinical samples. Subsequently, we discovered that rH promotes the polarisation of M1 macrophages but inhibits the polarisation of M2 macrophages. We also found that PAR-1 regulates macrophage polarisation, inhibiting cell proliferation, migration, invasion and angiogenic capacity.

CONCLUSION

rH inhibits macrophage polarisation towards the M2 type and PAR-1 regulates polarisation, proliferation, migration, invasion, and angiogenesis of DLBCL-associated macrophages.

The efficacy and safety of Hirudin plus Aspirin versus Warfarin in the secondary prevention of Cardioembolic Stroke due to Nonvalvular Atrial Fibrillation: A multicenter prospective cohort study

Background: To investigate the efficacy and safety of hirudin plus aspirin therapy compared with warfarin in the secondary prevention of cardioembolic stroke due to nonvalvular atrial fibrillation (NVAF). Methods: Patients with cardioembolic stroke due to NVAF were prospectively enrolled from 18 collaborating hospitals from Dec 2011 to June 2015. Fourteen days after stroke onset, eligible patients were assigned to the hirudin plus aspirin group (natural hirudin prescribed as the traditional Chinese medicine Maixuekang capsule, 0.75 g, three times daily, combined with aspirin 100 mg, once daily) or the warfarin group (dose-adjusted warfarin targeting international normalized ratio (INR) 2-3, with an initial daily dose of 1.25 mg). Patients were followed up at 1, 2, 3, 6, 9, and 12 months after stroke onset. Time in therapeutic range (TTR) was calculated according to Rosendaal methodology to evaluate the quality of INR management in the warfarin group. The primary efficacy endpoint was the recurrence of stroke within 12 months after stroke onset. Safety was assessed as the occurrence of the composite event "intracranial hemorrhage and other bleeding events, death, and other serious adverse events". The Cox proportional hazard model and Kaplan-Meier curve were used to analyze the efficacy and safety events. Results: A total of 221 patients entered final analysis with 112 patients in the hirudin plus aspirin group and 109 in the warfarin group. Over the whole duration of our study, TTR for patients taking warfarin was 66.5 % ± 21.5%. A significant difference was not observed in the recurrence of stroke between the two groups (3.57% vs. 2.75%; P = 0.728). The occurrence of safety events was significantly lower in the hirudin plus aspirin group (2.68% vs.10.09%; P = 0.024). The risk for efficacy event was similar between the two groups (hazard ratio (HR), 1.30; 95% confidence interval (CI), 0.29-5.80). The safety risk was significantly lower in the hirudin plus aspirin group (HR, 0.27; 95% CI, 0.07-0.95). Kaplan-Meier analysis revealed significant difference in the temporal distribution in safety events (P = 0.023) but not in stroke recurrence (P = 0.726). Conclusion: Significant difference in efficacy was not detected between warfarin group and hirudin plus aspirin group. Compared with warfarin, hirudin plus aspirin therapy had lower safety risk in the secondary prevention of cardioembolic stroke due to NVAF.

Hirudin variants production by genetic engineered microbial factory

Hirudin was discovered as an active anticoagulant in leech extracts almost 60 years ago. Since their initial discovery, hirudin and its variants have been produced with various anti-thrombotic, cancer cell inhibition, diabetic cataract treatment and anti-fatigue activities. Some hirudin variants have been approved for clinical use and released into the marketplace. Recent progress has seen made in relation to hirudin variants expressed in several well-established microbial hosts, including Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and others, with high levels of activity and yield. This review summarizes the current progress on hirudin production using microbial producers, and considers the outlook for future development.

Is there an alternative to systemic anticoagulation, as related to interventional biomedical devices?

To reduce the toxic effects, related clinical problems and complications such as bleeding disorders associated with systemic anticoagulation, it has been hypothesized that by coating the surfaces of medical devices, such as stents, bypass grafts, extracorporeal circuits, guide wires and catheters, there will be a significant reduction in the requirement for systemic anticoagulation or, ideally, it will no longer be necessary. However, current coating processes, even covalent ones, still result in leaching followed by reduced functionality. Alternative anticoagulants and related antiplatelet agents have been used for improvement in terms of reduced restenosis, intimal hyperphasia and device failure. This review focuses on existing heparinization processes, their application in clinical devices and the updated list of alternatives to heparinization in order to obtain a broad overview, it then highlights, in particular, the future possibilities of using heparin and related moieties to tissue engineer scaffolds.

Tissue factor, blood coagulation, and beyond: an overview

Emerging evidence shows a broad spectrum of biological functions of tissue factor (TF). TF classical role in initiating the extrinsic blood coagulation and its direct thrombotic action in close relation to cardiovascular risks have long been established. TF overexpression/hypercoagulability often observed in many clinical conditions certainly expands its role in proinflammation, diabetes, obesity, cardiovascular diseases, angiogenesis, tumor metastasis, wound repairs, embryonic development, cell adhesion/migration, innate immunity, infection, pregnancy loss, and many others. This paper broadly covers seminal observations to discuss TF pathogenic roles in relation to diverse disease development or manifestation. Biochemically, extracellular TF signaling interfaced through protease-activated receptors (PARs) elicits cellular activation and inflammatory responses. TF diverse biological roles are associated with either coagulation-dependent or noncoagulation-mediated actions. Apparently, TF hypercoagulability refuels a coagulation-inflammation-thrombosis circuit in “autocrine” or “paracrine” fashions, which triggers a wide spectrum of pathophysiology. Accordingly, TF suppression, anticoagulation, PAR blockade, or general anti-inflammation offers an array of therapeutical benefits for easing diverse pathological conditions.

Thrombin inhibitors from different animals

Venous and arterial thromboembolic diseases are still the most frequent causes of death and disability in high-income countries. Clinical anticoagulants are inhibitors of enzymes involved in the coagulation pathway, such as thrombin and factor X(a). Thrombin is a key enzyme of blood coagulation system, activating the platelets, converting the fibrinogen to the fibrin net, and amplifying its self-generation by the activation of factors V, VIII, and XI. Thrombin has long been a target for the development of oral anticoagulants. Furthermore, selective inhibitors of thrombin represent a new class of antithrombotic agents. For these reasons, a number of specific thrombin inhibitors are under evaluation for possible use as antithrombotic drugs. This paper summarizes old and new interests of specific thrombin inhibitors described in different animals.

Thrombin receptor (PAR-1) antagonists as novel antithrombotic agents

In addition to its central role in haemostasis and wound healing, thrombin activates platelets and smooth muscle cells by proteolytic activation of cell surface protease-activated receptor-1 (PAR-1), which is also known as the thrombin receptor. Thrombin is the most potent activator of human platelets and, as such, a thrombin receptor antagonist is likely to exert potent antithrombotic effect in platelet-rich arterial thrombosis. As thrombin receptor antagonism does not inhibit the ability of thrombin to generate fibrin, such an agent is likely to have less bleeding liability than conventional anticoagulants. The proof-of-concept of the antithrombotic effect of PAR-1 antagonists has been established in several non-human primate models. The current success of PAR-1 research is underscored by the advancement of two candidates into clinical trails for acute coronary syndrome by Schering-Plough and Eisai Company.

Desirudin dosing and monitoring in moderate renal impairment

Desirudin is a renally eliminated direct thrombin inhibitor approved to prevent venous thromboembolism. Empiric dosage adjustment and activated partial thromboplastin time (aPTT) monitoring in patients with moderate renal impairment are recommended, but supportive data are lacking. The objective of this study was to evaluate appropriate desirudin dosing in moderate renal impairment and the effect of desirudin on aPTT in moderate renal impairment. Desirudin plasma concentration and aPTT data were extracted from 6 studies. Participants with normal renal function or moderate renal impairment (creatinine clearance [ClCr] 31-60 mL/min) were included. Pharmacokinetic and Monte Carlo simulations were done. After administration of desirudin 15 mg every 12 hours subcutaneously (SC) to steady state, peak desirudin concentrations were 35 and 47 nmol/L in the normal and moderate renal function groups, respectively. Monte Carlo simulations found median 2-hour C(max) concentrations of 51.7 nmol/L in normal renal function and 52.4 nmol/L in moderate renal impairment. Desirudin exhibits a linear relationship when the square root of desirudin concentration is plotted versus the aPTT ratio (r(2) = 0.76). These analyses support the dosing of desirudin at 15 mg every 12 hours SC without aPTT monitoring in patients with moderate renal impairment.

Combined administration of barbourin--albumin and hirudin--albumin fusion proteins limits fibrin(ogen) deposition on the rabbit balloon-injured aorta

INTRODUCTION

There are continuing needs for new antithrombotic agents and procedures. We hypothesized that the slowly cleared recombinant fusion proteins barbourin--albumin (BLAH6) and hirudin--albumin (HLAH6) would be effective in limiting fibrin(ogen) and/or platelet deposition in a rabbit model of arterial injury.

MATERIALS AND METHODS

Recombinant fusion proteins were expressed in Pichia pastoris fermenter cultures and purified by nickel-chelate affinity chromatography. They were injected intravenously into rabbits prior to blood sampling and platelet aggregometry, assessment of deposition of 125I-fibrin(ogen) and 51Cr-platelet onto the balloon-injured thoracic aorta, electron microscopy (EM) and immunohistochemistry of aortic sections, and determination of bleeding time following a standardized ear incision.

RESULTS AND CONCLUSIONS

BLAH6 administration elicited a dose- and time-dependent inhibition of platelet aggregation in post-injection whole blood samples, and reduced both fibrin(ogen) and platelet deposition on the injured aorta, although the former effect was both more durable and more significant than the latter. In contrast, HLAH6 injection reduced fibrin(ogen) but not platelet deposition. Doses of the two proteins ineffective in preventing fibrin(ogen) deposition when given alone were effective when combined, suggesting at least additive effects. Immunohistochemistry and EM supported the radioactive deposition studies, while bleeding times were decreased with combined BLAH6 and HLAH6 administration compared to HLAH6 alone in a rabbit ear bleeding model. The data show that these fusion proteins exert an antithrombotic effect in vivo and may indicate that combined low-dose administration of antiplatelet and antithrombin agents could offer safety advantages in the treatment of thrombosis.