Towards safer thrombolytic therapy

Escin avoids hemorrhagic transformation in ischemic stroke by protecting BBB through the AMPK/Cav-1/MMP-9 pathway

BACKGROUND

Hemorrhagic transformation (HT) seriously affects the clinical application of recombinant tissue plasminogen activator (rt-PA). The main strategy for combating HT is to keep the blood-brain barrier (BBB) stable. Escin is the active ingredient of Aesculus hippocastanum and a natural mixture of triterpene saponins, and may play a part in mitigation of HT.

PURPOSE

This study sought to investigate the effect of Escin in improving rt-PA-induced HT, explore possible mechanisms, and provide new ideas for the treatment of clinical HT.

STUDY DESIGN AND METHODS

In in vivo experiments, transient middle cerebral artery occlusion (tMCAO) was undertaken in 6-week-old and 12-month-old mice, and rt-PA was administered to induce HT injury. The inhibitory effect of Escin on HT and its protective effect on neurobehavior, the BBB, and cerebrovascular endothelial cells was determined. In in vitro experiments, bEnd.3 cells were injured by oxygen-glucose deprivation/reperfusion (OGD/R) and rt-PA. The protective effect of Escin was measured by the CCK8 assay, release of lactate dehydrogenase (LDH), and expression of tight junction (TJ) proteins. In mechanistic studies, the effect of Escin on the adenosine monophosphate-activated kinase / caveolin-1 / matrix metalloprotease-9 (AMPK/Cav-1/MMP-9) pathway was investigated by employing AMPK inhibitor and Cav-1 siRNA.

RESULTS

In mice suffering from ischemia, rt-PA caused HT as well as damage to the BBB and cerebrovascular endothelial cells. Escin reduced the infarct volume, cerebral hemorrhage, improved neurobehavioral deficits, and maintained BBB integrity in rt-PA-treated tMCAO mice while attenuating bEnd.3 cells damage caused by rt-PA and OGD/R injury. Under physiological and pathological conditions, Escin increased the expression of p-AMPK and Cav-1, leading to decreased expression of MMP-9, which further attenuated damage to cerebrovascular endothelial cells, and these effects were verified with AMPK inhibitor and Cav-1 siRNA.

CONCLUSION

We revealed important details of how Escin protects cerebrovascular endothelial cells from HT, these effects were associated with the AMPK/Cav-1/MMP-9 pathway. This study provides experimental foundation for the development of new drugs to mitigate rt-PA-induced HT and the discovery of new clinical application for Escin.

MiR-101 Protects Against the Cerebral I/R Injury Through Regulating JAK2/STAT3 Signaling Pathway

BACKGROUND

Ischemic stroke is a devastating disease with very limited therapeutics. Although miR-101 has been reported to play crucial roles in various human diseases, its role in ischemic stroke remains unclear.

METHODS

Ischemia-reperfusion (I/R) injury neuronal cells and rat model with I/R injury were constructed. Viability and apoptosis of I/R model cells with miR-101 overexpression or downregulation were evaluated. Potential targets of miR-101 were predicted using miRNA database microRNA.org and confirmed using luciferase reporter assays. Meanwhile, JAK2 and p-STAT3 protein levels were evaluated by Western blot. In addition, rescue experiments (silencing of JAK2) were applied to determine the role of miR-101 in cerebral I/R injury.

RESULTS

MiR-101 was significantly downregulated in OGD/R-induced neuronal cells and brain tissues with I/R injury. MiR-101 overexpression (miR-101 mimics) significantly promoted viability and inhibited apoptosis of OGD/R-induced neuronal cells in vitro and efficiently protected rats from ischemic brain injury in vivo. By contrast, miR-101 inhibitor exacerbated growth defect, apoptosis, and ischemic brain injury. Luciferase reporter assay indicated that JAK2 was a direct target of mIR-101, and JAK2 silencing effectively reversed the miR-101 inhibitor-induced neuronal cell apoptosis in vitro and reduced cerebral infarction volume in vivo.

CONCLUSION

Our study demonstrated that miR-101 efficiently protected neuronal cells from apoptosis and ischemic brain injury through regulating the JAK2/STAT3 signaling pathway, suggesting that miR-101 might be a potential target for treatment of ischemic stroke.

Danhong Injection Combined With t-PA Improves Thrombolytic Therapy in Focal Embolic Stroke

Background: Hemorrhagic transformation, neurotoxicity, short treatment time windows, and other defects are considered as the major limitations for the thrombolytic therapy. This study is devoted to figure out whether Danhong injection (DHI) combined with tissue-plasminogen activator (t-PA) could extend the treatment time windows and ameliorate brain injury, hemorrhagic complication and BBB disruption after focal embolic stroke. Methods:In vitro, the combined concentrations of DHI and t-PA were added to wells reacted with plasminogen and D-Val-Leu-Lys-AMC. The optimum ratio of the combination of DHI plus t-PA was explored by detecting relative fluorescent. In vivo experiments, we firstly investigated the optimal dose of t-PA and Danhong injection for focal embolic stroke. The neurological deficit score, infarct volume and brain edema were assessed. Secondly, we proved that the combination group extended the thrombolytic window for treatment of focal embolic stroke. The neurological deficit score, infarct volume, brain edema and hemorrhagic complication were assessed, while levels of BAX, Bcl-2 and caspase-3 in brain tissue were analyzed by real-time polymerase chain reaction. Finally, to ask whether combination therapy with DHI plus t-PA protected the blood-brain barrier in a rat model of focal embolic stroke, neurological deficit score, ELISA, RT-PCR, western blot and fluorescence were used to detect the indicators of blood-brain barrier, such as tight junction protein, blood-brain barrier permeability and related gene expression. Results:In vitro, plasmin activity assays showed that the combination of t-PA with DHI at about 1:1.6 w/v ratio increased by almost 1.4-fold the plasmin-generating capability of t-PA. In vivo experiments, the results showed that the combination of Danhong injection (4 mL/kg) and t-PA (2.5 mg/kg) could extend the t-PA treatment time windows to 4.5 h. And the combination t-PA (2.5 mg/kg) with DHI (4 mL/kg) ameliorated neurological score, cerebral infarction, brain edema, brain hemorrhage, and BBB disruption. Conclusion: Combination therapy with Danhong injection (4 mL/kg) plus t-PA (2.5 mg/kg) could extend the t-PA treatment time windows to 4.5 h, ameliorate BBB disruption, reduce infarction, brain swelling and hemorrhage after ischemic stroke.

Structure and Function of Trypsin-Loaded Fibrinolytic Liposomes

Protease encapsulation and its targeted release in thrombi may contribute to the reduction of haemorrhagic complications of thrombolysis. We aimed to prepare sterically stabilized trypsin-loaded liposomes (SSL_T) and characterize their structure and fibrinolytic efficiency. Hydrogenated soybean phosphatidylcholine-based SSL_T were prepared and their structure was studied by transmission electron microscopy combined with freeze fracture (FF-TEM), Fourier transform infrared spectroscopy (FT-IR), and small-angle X-ray scattering (SAXS). Fibrinolytic activity was examined at 45, 37, or 24°C on fibrin or plasma clots with turbidimetric and permeation-driven lysis assays. Trypsin was shown to be attached to the inner surface of vesicles (SAXS and FF-TEM) close to the lipid hydrophilic/hydrophobic interface (FT-IR). The thermosensitivity of SSL_T was evidenced by enhanced fibrinolysis at 45°C: time to reduce the maximal turbidity to 20% decreased by 8.6% compared to 37°C and fibrin degradation product concentration in the permeation lysis assay was 2-fold to 5-fold higher than that at 24°C. SSL_T exerted its fibrinolytic action on fibrin clots under both static and dynamic conditions, whereas plasma clot dissolution was observed only in the permeation-driven assay. The improved fibrinolytic efficiency of SSL_T under dynamic conditions suggests that they may serve as a novel therapeutic candidate for dissolution of intravascular thrombi, which are typically exposed to permeation forces.

Bleeding related to disturbed fibrinolysis

The components and reactions of the fibrinolysis system are well understood. The pathway has fewer reactants and interactions than coagulation, but the generation of a complete quantitative model is complicated by the need to work at the solid‐liquid interface of fibrin. Diagnostic tools to detect disease states due to malfunctions in the fibrinolysis pathway are also not so well developed as is the case with coagulation. However, there are clearly a number of inherited or acquired pathologies where hyperfibrinolysis is a serious, potentially life‐threatening problem and a number of antifibrinolytc drugs are available to treat hyperfibrinolysis. These topics will be covered in the following review.

Upper Limb Ischemia: 20 Years Experience from a Single Center

The objective of this study was to review a single center's experience of upper limb revascularization over 20 years.

All patients undergoing operative or endovascular upper limb revascularization between June 1983 and July 2003 were identified.

One hundred eighty-four upper limb revascularization procedures were carried out on 172 patients. Sixty-one patients had a thromboembolic event (35%), 53 patients presented with a traumatic vascular injury (31%), and 29 patients had symptoms of chronic atherosclerotic upper limb ischemia (17%). Fifteen patients had subclavian steal syndrome, eight patients had thoracic outlet compression, and six patients had iatrogenic injuries of the upper limb arteries.

Fifty-five thromboembolectomies were performed, 37 under locoregional anesthesia. Ten patients (18.2%) died from cardiopulmonary causes following embolectomy.

Fifteen reversed saphenous vein bypass grafts were performed for traumatic damage. Twenty-seven patients had a primary repair, and five required a vein patch. One patient subsequently had an arm amputation, and two patients died.

Twelve patients presenting with chronic arm ischemia had a subclavian angioplasty, 12 patients had a proximal bypass, and in 5 patients, stenoses were stented. The mortality in this group was 6.9% (2 of 29).

The mortality for upper limb revascularization was 8.7%. Almost all deaths occurred after upper limb embolectomy, and the mortality of this procedure was similar to that of lower limb embolectomy. Deaths were the result of cardiac comorbidity, and this should be actively sought and treated if outcomes are to improve.

Arterial Embolisms and Thrombosis in Upper Extremity Ischemia

Objective:

Upper extremity ischemia (UEI) is an uncommon condition that can lead to permanent disability. There is a limited understanding of the etiology, management, and outcomes of the disease.

Methods:

We retrospectively reviewed the charts of all patients who were diagnosed with “embolism and/or thrombosis of arteries of upper extremity” at our institution from January 2005 to December 2013.

Results:

Patients diagnosed with embolisms were older ( P < .001), more likely to undergo thromboembolectomy ( P < .001), had higher rates of hypertension ( P = .001), and had longer lengths of hospital stay ( P = .002). There were no significant differences in complications or mortality at 30 days and up to 1 year.

Conclusion:

At our center, embolism was found to be the most common etiology for UEI followed by thrombosis and stenosis. Patients presented with embolism were older, were more likely to undergo thromboembolectomy, and had higher rates of hypertension and longer hospital stays.

Anticoagulation drug therapy: a review

Historically, most patients who required parenteral anticoagulation received heparin, whereas those patients requiring oral anticoagulation received warfarin. Due to the narrow therapeutic index and need for frequent laboratory monitoring associated with warfarin, there has been a desire to develop newer, more effective anticoagulants. Consequently, in recent years many novel anticoagulants have been developed.

The emergency physician may institute anticoagulation therapy in the short term (e.g. heparin) for a patient being admitted, or may start a novel anticoagulation for a patient being discharged. Similarly, a patient on a novel anticoagulant may present to the emergency department due to a hemorrhagic complication. Consequently, the emergency physician should be familiar with the newer and older anticoagulants. This review emphasizes the indication, mechanism of action, adverse effects, and potential reversal strategies for various anticoagulants that the emergency physician will likely encounter.

Successful treatment of ST elevation myocardial infarction caused by septic embolus with the use of a thrombectomy catheter in infective endocarditis

A 71-year-old patient suffered a transmural (ST elevation) myocardial infarction (MI) as a result of a septic embolus from an infected tissue aortic valve replacement. Following failed fibrinolysis, his MI was successfully treated with thrombectomy using an export catheter. He suffered bleeding complications following the administration of tenectaplase and required aortic valve and root replacement due to ongoing systemic embolisation.

Historical perspective and future direction of thrombolysis research: the re-discovery of plasmin

Two issues have held the focus of thrombolysis research for over 50 years, namely, choosing between a plasminogen activator (PA) or plasmin as the best therapeutic agent and choosing between systemic or local administration. The original plasmin product of the 1950s was both ineffective and contaminated with PA, and catheter technology was not yet developed for routine clinical use. For decades, clinical practice has focused on PA and systemic administration, but today, PAs are often administered by catheter into thrombosed vessels, notably for peripheral arterial and graft occlusion and deep vein thrombosis, and increasingly for acute ischaemic stroke. Despite using catheter-delivered therapy, bleeding complications still occur, most severely expressed as symptomatic intracranial haemorrhage. New experimental data indicate that we should now reconsider plasmin as a viable, even preferable, thrombolytic agent. Plasmin requires catheter delivery to achieve thrombolysis, but this technical issue has been solved with modern technology and widespread presence of interventional suites. After local administration, plasmin will lyse thrombi; thereafter, any plasmin in the circulation will be rapidly neutralised. Pre-clinical studies confirm that plasmin has marked haemostatic safety advantage over t-PA. After more than 50 years, the field has come full circle, and plasmin as the thrombolytic agent and catheter use for local delivery of agent may represent a step forward in thrombolytic therapy.

Improving reperfusion therapy for acute ischaemic stroke

BACKGROUND

The first generation of clinical reperfusion treatment, intravenous (IV) fibrinolysis with tissue plasminogen activator (tPA), was a transformative breakthrough in stroke care, but is far from ideal.

OBJECTIVES

TO survey emerging strategies to increase the efficacy and safety of cerebral reperfusion therapy.

METHODS

Narrative review.

RESULTS AND CONCLUSIONS

Innovative IV pharmacologic reperfusion strategies include: extending IV tPA use to patients with mild deficits; developing novel fibrinolytic agents (tenecteplase, desmetolplase, plasmin); using ultrasound to enhance enzymatic fibrinolysis; combination clot lysis therapies (fibrinolytics with GPIIb/IIIa agents or direct thrombin inhibitors); co-administration of MMP-9 inhibitors to deter haemorrhagic transformation; and prehospital neuroprotection to support threatened tissues until reperfusion. Endovascular recanalisation strategies are rapidly evolving, and include intra-arterial fibrinolysis, mechanical clot retrieval, suction thrombectomy, and primary stenting. Combined approaches appear especially promising, using IV fibrinolysis to rapidly initiate reperfusion, mechanical endovascular treatment to debulk large, proximal thrombi, and intra-arterial (IA) fibrinolysis to clear residual distal thrombus elements and emboli.

Annexin A2: a tissue plasminogen activator amplifier for thrombolytic stroke therapy

Hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and the short treatment time window comprise major challenges for thrombolytic therapy. Improving tissue plasminogen activator therapy has become one of the highest priorities in the stroke field. Recent efforts have been aimed at identifying new strategies that might enhance the thrombolytic efficacy of tissue plasminogen activator at the same time as reducing its associated complications related to hemorrhage and neurotoxicity. We believe that the combination of low-dose tissue plasminogen activator with recombinant annexin A2 (a tissue plasminogen activator and plasminogen coreceptor) might constitute a promising approach. Our pilot study using a focal embolic stroke model in rats supports this hypothesis.

Drug delivery by red blood cells: vascular carriers designed by mother nature

IMPORTANCE OF THE FIELD

Vascular delivery of several classes of therapeutic agents may benefit from carriage by red blood cells (RBC), for example, drugs that require delivery into phagocytic cells and those that must act within the vascular lumen. The fact that several protocols of infusion of RBC-encapsulated drugs are now being explored in patients illustrates a high biomedical importance for the field. AREAS COVERED BY THIS REVIEW: Two strategies for RBC drug delivery are discussed: encapsulation into isolated RBC ex vivo followed by infusion in compatible recipients and coupling therapeutics to the surface of RBC. Studies of pharmacokinetics and effects in animal models and in human studies of diverse therapeutic enzymes, antibiotics and other drugs encapsulated in RBC are described and critically analyzed. Coupling to RBC surface of compounds regulating immune response and complement, affinity ligands, polyethylene glycol alleviating immune response to donor RBC and fibrinolytic plasminogen activators are described. Also described is a new, translation-prone approach for RBC drug delivery by injection of therapeutics conjugated with fragments of antibodies providing safe anchoring of cargoes to circulating RBC, without need for ex vivo modification and infusion of RBC.

WHAT THE READER WILL GAIN

Readers will gain historical perspective, current status, challenges and perspectives of medical applications of RBC for drug delivery.

TAKE HOME MESSAGE

RBC represent naturally designed carriers for intravascular drug delivery, characterized by unique longevity in the bloodstream, biocompatibility and safe physiological mechanisms for metabolism. New approaches for encapsulating drugs into RBC and coupling to RBC surface provide promising avenues for safe and widely useful improvement of drug delivery in the vascular system.

Chemical conjugation of urokinase to magnetic nanoparticles for targeted thrombolysis

Thrombolytic therapy is an important treatment for thrombosis, a life-threatening condition in cardiovascular diseases. However, the traditional thrombolytic therapies have often been associated with the risk of severe bleeding. By conjugating urokinase with magnetic nanoparticles (MNPs), we have presented a strategy to control thrombolysis within a specific site. The covalent bioconjugate of urokinase and dextran-coated MNPs was synthesized and isolated. Thrombolysis by the conjugate was studied under a magnetic field in a rat arteriovenous shunt thrombosis model. The magnetic field was generated by two AlNiCo permanent magnets around the site of thrombus. The magnetic field enhanced the thrombolytic efficacy of the conjugate by 5-fold over urokinase with no reduction in plasma fibrinogen and little prolonged bleeding time. It suggested that thrombolysis had been specifically directed to the desired site by the magnetic carrier under the magnetic field. Additionally, the conjugate had a longer half-life than urokinase in circulation.

Phase 1 study of human plasma-derived plasmin (TAL-05-00018) in hemodialysis graft occlusion

INTRODUCTION

Hemodialysis grafts often fail because of stenosis at the venous anastomosis resulting in thrombosis. Percutaneous intervention involves thrombolysis with plasminogen activators, mechanical removal of thrombus, and angioplasty of the stenotic lesions.

OBJECTIVES

This article describes a phase I trial using plasmin (human) TAL 05-00018, a direct-acting fibrinolytic agent, to evaluate safety and, secondarily, to establish effective thrombolytic dosing.

PATIENTS/METHODS

Six cohorts of five patients with acute HD graft occlusion documented by fistulagrams were treated with increasing dosages of plasmin (1, 2, 4, 8, 12, and 24 mg) infused within the graft over 30 min via two criss-crossed pulse-spray catheters. The primary efficacy endpoint was at least 50% thrombolysis, as determined by fistulography.

RESULTS

There was no significant change in plasma alpha-2 antiplasmin or fibrinogen concentration, major bleeding did not occur, and there were no deaths. Serious adverse events in four patients were not related to the study drug. There was a dose-response relationship for the primary efficacy endpoint, all five subjects receiving 24 mg achieving more than 75% lysis.

CONCLUSION

This first phase I study of plasmin (human) TAL 05-00018, infused into thrombosed HD grafts, documents safety at all doses and an effective thrombolytic dosage of 24 mg indicating that further investigation into locally delivered plasmin is warranted.

A first-in-human phase I trial of locally delivered human plasmin for hemodialysis graft occlusion

BACKGROUND

Hemodialysis (HD) grafts often fail because of stenosis at the venous anastomosis and thrombotic occlusion. Percutaneous management relies on thrombolysis with plasminogen activators, mechanical removal of thrombus, and angioplasty of the stenotic lesion.

OBJECTIVES

This report describes a phase I trial using Plasmin (Human) TAL 05-00018, a direct-acting fibrinolytic agent, to evaluate safety and, secondarily, to establish effective thrombolytic dosing.

PATIENTS/METHODS

Six cohorts of five patients with acute HD graft occlusion documented by angiography were treated with escalating dosages of plasmin (1, 2, 4, 8, 12, and 24 mg) infused over 30 min via criss-crossed pulse-spray catheters within the graft. The primary efficacy endpoint was > or =50% thrombolysis, as determined by comparison of pre-plasmin and 30-min post-plasmin fistulograms.

RESULTS

Of 31 subjects who received study drug (safety population), one withdrew and 30 completed the trial (evaluable for efficacy). There was no significant change in plasma alpha-2 antiplasmin or fibrinogen concentration, major bleeding did not occur, and there were no deaths. Serious adverse events in four patients were not related to the study drug. There was a dose-response relationship for the primary efficacy endpoint, all five subjects receiving 24 mg achieving >75% lysis.

CONCLUSIONS

This first phase I study of Plasmin (Human) TAL 05-00018, infused into thrombosed HD grafts, documents safety at dosages of 1-24 mg and an effective thrombolytic dosage of 24 mg. The results establish a foundation for further clinical study of catheter-based plasmin administration in thrombotic disorders.

Tissue-type plasminogen activator as a therapeutic target in stroke

BACKGROUND

Ischemic stroke is a leading cause of morbidity and mortality worldwide and recombinant human tissue-type plasminogen activator (tPA) is the prominent therapeutic among very few therapeutics used in its treatment. Due to complications attributed to the drug, most notably transformation of ischemia to hemorrhage, tPA is only used in a small number of ischemic stroke cases, albeit significantly more often in specialized stroke centers.

OBJECTIVE

What are the mechanisms of tPA action and side effects in ischemic stroke, and can the knowledge about these mechanisms aid in making tPA a more efficacious and safe therapeutic or in developing alternative therapeutics?

METHODS

tPA use and alternative/combination therapies in acute ischemic stroke treatment are summarized. The review focuses on literature concerning tPA neurotoxicity and its implications for further development of tPA as a stroke therapeutic.

RESULTS/CONCLUSION

Exogenously administered recombinant tPA and endogenous tPA have both turned into promising therapeutic targets for the stroke patient.

A phase I trial of alfimeprase for peripheral arterial thrombolysis

PURPOSE

To evaluate the safety profile, pharmacokinetics, and thrombolytic activity of alfimeprase, a novel direct-acting thrombolytic agent, in patients with chronic peripheral arterial occlusion (PAO).

MATERIALS AND METHODS

In this multicenter, open-label, single-dose, dose-escalation study, 20 patients with worsening symptoms of lower extremity ischemia within 6 months of enrollment were treated with alfimeprase in five escalating dose cohorts (0.025 mg/kg, 0.05 mg/kg, 0.1 mg/kg, 0.3 mg/kg, and 0.5 mg/kg) by means of intraarterial and sometimes intrathrombic pulsed infusion. The primary endpoint was safety assessed by adverse event rates. Additional safety assessments included vital sign monitoring, serum chemistry testing, hematologic testing, and coagulation testing for 28 days after the procedure, as well as alpha2-macroglobulin and antialfimeprase antibody testing for as long as 3 months after treatment. Pharmacokinetic parameters were evaluated with use of an assay that measures free and alpha2-macroglobulin-bound (ie, total) alfimeprase.

RESULTS

No patient experienced a hemorrhagic adverse event. Mean plasminogen and fibrinogen concentrations were not substantially altered by treatment. Three transient treatment-related adverse events were reported in the same patient: one incidence each of increased blood fibrinogen level, skin rash, and headache. All three adverse events were graded as mild. The pharmacokinetic profile of alfimeprase suggested that the half-life for total alfimeprase ranges from 11 to 54 minutes (median, 25 min) in patients with PAO. The serum alpha2-macroglobulin concentrations decreased transiently in a dose response-like manner between 12 and 24 hours and returned to within normal limits approximately 14 days after alfimeprase exposure.

CONCLUSIONS

Alfimeprase in doses as high as 0.5 mg/kg was generally well-tolerated in patients with chronic PAO. No bleeding complications were noted. The stable fibrinogen concentrations suggest that the activity of alfimeprase may be limited to the target thrombus. Alfimeprase holds the potential to achieve dissolution of thrombus with a diminished risk of hemorrhage.

Extending reperfusion therapy for acute ischemic stroke: emerging pharmacological, mechanical, and imaging strategies

BACKGROUND AND PURPOSE

Reperfusion is the most beneficial of all therapeutic strategies for acute ischemic stroke. However, the standard cerebral reperfusion treatment of the first decade of the reperfusion era, noncontrast computed tomography (CT)-guided, < or =3 hours, intravenous tissue plasminogen activator, has many limitations. This review surveys emerging strategies that have the potential to extend cerebral reperfusion therapy to larger numbers of patients.

SUMMARY OF REVIEW

Innovative intravenous pharmacological reperfusion strategies include novel fibrinolytic agents (tenecteplase, reteplase, desmetolplase, plasmin, and microplasmin), glycoprotein (GP) IIb/IIIa antagonists with platelet disaggregating effects (abciximab and tirofiban), combination therapies to improve efficacy of clot lysis (fibrinolytics and GP IIb/IIIa agents, and fibrinolytics and direct thrombin inhibitors), increase the time window for clot lysis (fibrinolytics and neuroprotectants), and reduce the frequency of hemorrhagic complications (fibrinolytics and vasoprotectants), and externally applied ultrasound to enhance enzymatic fibrinolysis. Promising intra-arterial pharmacological reperfusion approaches include novel fibrinolytic agents, combined intravenous and intra-arterial fibrinolysis, and combined fibrinolytics and GP IIb/IIIa agents. Emerging endovascular mechanical reperfusion strategies include intra-arterial thrombectomy (clot retrieval devices and suction thrombectomy devices), mechanical disruption (micro-guidewire passage, laser photoacoustic emulsification, and primary intracranial angioplasty), and augmented fibrinolysis by endovascular ultrasound. Multimodal imaging, with magnetic resonance (MR) or CT, can rapidly assess infarct core, penumbra, site of vessel occlusion, and tissue hemorrhagic propensity, enabling improved selection of patients for reperfusion therapy beyond any arbitrary fixed time window.

CONCLUSIONS

Therapeutic reperfusion is emerging as a treatment strategy of remarkable power and scope for rescuing patients experiencing acute brain ischemia, applicable within and beyond the 3-hour time window.

Lung endothelium targeting for pulmonary embolism thrombolysis

BACKGROUND

Pulmonary embolism occurs frequently in hospitalized patients. Thrombolytic therapy, currently used as the major treatment, has often been associated with severe bleeding complications and has thereby been life-threatening. We have developed a novel therapeutic method based on our newly created pulmonary endothelium-specific antibody.

METHODS AND RESULTS

We isolated membrane proteins of rat pulmonary vascular luminal endothelium and obtained a monoclonal antibody, RE8F5, which antigen was uniquely expressed by the pulmonary capillary endothelium. In vivo biodistribution showed that RE8F5 and its urokinase conjugate were rapidly and specifically accumulated in lung. Urokinase and the conjugate were compared in rats with pulmonary, hepatic, and lower-limb embolus. In a pulmonary embolus model, the conjugate exhibited 12-fold enhanced thrombolytic potency over urokinase, whereas plasma fibrinogen and bleeding time were unaffected. In 2 other models, no significant thrombolysis was induced by the conjugate. In contrast, thrombolysis by urokinase was found to be comparable to the pulmonary embolus model. In addition, urokinase caused significant consumption of fibrinogen in all experiments.

CONCLUSIONS

These data show that urokinase equipped with lung endothelium-specific antibody is an ideal treatment for pulmonary embolism, with a high efficacy of thrombolysis and low risk of bleeding.