Influence of thrombin-activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 gene polymorphisms on tissue-type plasminogen activator-induced recanalization in ischemic stroke patients

High thrombin-activatable fibrinolysis inhibitor expression in thrombi from stroke patients in elevated estrogen states

BACKGROUND

The risk of acute ischemic stroke (AIS) associated with high estrogen states, including pregnant patients and those using oral contraceptives, has been well documented. We described the histological composition of thrombi collected in these cases.

METHODS

From a prospective tissue registry (STRIP registry) of thrombi retrieved during mechanical thrombectomy for AIS, we identified 5 patients with high estrogen states: 1 post-partum patient, 1 undergoing hormone replacement therapy and 3 consuming oral contraceptive pills. Five male control patients were randomly chosen matched by age. Immunohistochemistry for CD42b (platelets), von Willebrand factor (vWF), thrombin-activatable fibrinolysis inhibitor (TAFI), fibrinogen and plasminogen activator inhibitor-1 (PAI-1) was performed. Expression was quantified using Orbit Image Software. Student's t-test was performed as appropriate.

RESULTS

Mean TAFI content for the high estrogen state group was higher than controls (25.6 ± 11.9% versus 9.3 ± 9.0%, p = 0.043*). Mean platelet content for the high estrogen state group was lower than controls (41.7 ± 10.6% versus 61.8 ± 12.9%, p = 0.029*). No significant difference was found in vWF, fibrinogen and PAI-1 expression. Mean time to recanalize was higher in the high estrogen state group compared to the control group (57.8 ± 27.6 versus 22.6 ± 11.4 min, p = 0.0351*). The mean number of passes required was higher in the high estrogen group compared to controls 4.6 versus 1.2, p = 0.0261*).

CONCLUSIONS

TAFI expression, a powerful driver of thrombosis, was significantly higher in stroke thrombi among patients with high estrogen states compared to controls.

Profibrinolytic effects of rivaroxaban are mediated by thrombin-activatable fibrinolysis inhibitor and are attenuated by a naturally occurring stabilizing mutation in enzyme

Rivaroxaban is a direct factor Xa inhibitor, recently implemented as a favorable alternative to warfarin in anticoagulation therapy. Rivaroxaban effectively reduces thrombin generation, which plays a major role in the activation of thrombin activatable fibrinolysis inhibitor (TAFI) to TAFIa. Based on the antifibrinolytic role of TAFIa, we hypothesized that rivaroxaban would consequently induce more rapid clot lysis. In vitro clot lysis assays were used to explore this hypothesis and additionally determine the effects of varying TAFI levels and a stabilizing Thr325Ile polymorphism (rs1926447) in the TAFI protein on the effects of rivaroxaban. Rivaroxaban was shown to decrease thrombin generation, resulting in less TAFI activation, thus enhancing lysis. These effects were also shown to be less substantial in the presence of greater TAFI levels or the more stable Ile325 enzyme. These findings suggest a role for TAFI levels and the Thr325Ile polymorphism in the pharmacodynamics and pharmacogenomics of rivaroxaban.

Carboxypeptidase U (TAFIa) Is Rapidly Activated and Deactivated Following Thrombolysis and Thrombectomy in Stroke Patients

The antifibrinolytic enzyme carboxypeptidase U (CPU, TAFIa, CPB2) is an appealing target for the treatment of acute ischemic stroke (AIS). Increased insights in CPU activation and inactivation during thrombolysis (rtPA) with or without endovascular thrombectomy (EVT) are required to develop CPU inhibitors as profibrinolytic agents with optimal benefits/risks. Therefore, CPU kinetics during ischemic stroke treatment were evaluated. AIS patients with documented cerebral artery occlusion receiving rtPA (N = 20) or rtPA + EVT (N = 16) were included. CPU activation during thrombolysis was measured by an ultrasensitive HPLC-based CPU activity method and by an ELISA measuring both CPU and inactivated CPU (CPU + CPUi). Intravenous blood samples were collected at admission and throughout the first 24 h. Additional in situ blood samples were collected in the rtPA + EVT cohort proximal from the thrombus. The NIHSS score was determined at baseline and 24 h. CPU activity and CPU + CPUi levels increased upon rtPA administration and reached peak values at the end of thrombolysis (1 h). High inter-individual variability was observed in both groups. CPU activity decreased rapidly within 3 h, while CPU + CPUi levels were still elevated at 7 h. CPU activity or CPU + CPUi levels were similar in in situ and peripheral samples. No correlation between CPU or CPU + CPUi and NIHSS or thrombus localization was found. The CPU system was rapidly activated and deactivated following thrombolysis and thrombectomy in stroke patients, suggesting that a CPU inhibitor would have to be administered during rtPA infusion and over the next few hours. The high CPU generation variability suggests that some patients may not respond to the treatment. EudraCT number 2017-002760-41.

Pharmacogenetics studies in stroke patients treated with rtPA: a review of the most interesting findings

Recombinant tissue-plasminogen activator (rtPA) is the only drug used during the acute phase of stroke. Despite its important benefits, a percentage of patients suffer symptomatic hemorrhagic transformations or a lack of early recanalization rates. These undesirable effects are associated with acute neurological and long-term functional deterioration. For the past 20 years, pharmacogenetic studies have tried to find the genetic risk factors associated with rtPA response. Most of these studies have used a gene-candidate strategy; however, recent genome-wide association studies have emerged indicating that genetic predisposition could modulate rtPA response. This review summarizes the most interesting findings in this field, including which genes and genetic variations are associated with hemorrhagic transformations and recanalization rates after thrombolytic therapy.

Carboxypeptidase U (CPU, TAFIa, CPB2) in Thromboembolic Disease: What Do We Know Three Decades after Its Discovery?

Procarboxypeptidase U (proCPU, TAFI, proCPB2) is a basic carboxypeptidase zymogen that is converted by thrombin(-thrombomodulin) or plasmin into the active carboxypeptidase U (CPU, TAFIa, CPB2), a potent attenuator of fibrinolysis. As CPU forms a molecular link between coagulation and fibrinolysis, the development of CPU inhibitors as profibrinolytic agents constitutes an attractive new concept to improve endogenous fibrinolysis or to increase the efficacy of thrombolytic therapy in thromboembolic diseases. Furthermore, extensive research has been conducted on the in vivo role of CPU in (the acute phase of) thromboembolic disease, as well as on the hypothesis that high proCPU levels and the Thr/Ile325 polymorphism may cause a thrombotic predisposition. In this paper, an overview is given of the methods available for measuring proCPU, CPU, and inactivated CPU (CPUi), together with a summary of the clinical data generated so far, ranging from the current knowledge on proCPU concentrations and polymorphisms as potential thromboembolic risk factors to the positioning of different CPU forms (proCPU, CPU, and CPUi) as diagnostic markers for thromboembolic disease, and the potential benefit of pharmacological inhibition of the CPU pathway.

Effects of arterial hemorrhage speed on the blood coagulation/fibrinolysis system and hemodynamics in rats

: The effects of rapid hemorrhage on coagulopathy have been reported. However, the effects of different hemorrhage speeds on the blood coagulation/fibrinolysis system have not been investigated. This study aimed to compare different hemorrhage speeds for clarifying their effects on the coagulation/fibrinolysis system and circulation disorders in rats. Male Sprague-Dawley rats (301-396 g) were randomly assigned to five groups depending on hemorrhage speed and length of procedure: first, rapid (1.4 ml/min, 30-min bleeding); second, rapid-L (1.4 ml/min, 30-min bleeding and observation until 6 h); third, slow (0.1 ml/min, intermittently, 6-h bleeding); fourth, control (30-min observation); and fifth, control-L (6-h observation). Hemorrhage was induced by withdrawing blood until 40% of the estimated blood volume from the femoral artery. We measured vital signs, hematology, general chemistry, blood gas status, coagulation parameters, fibrinolytic markers [tissue-type plasminogen activator and plasminogen activator inhibitor one (PAI-1)], vascular endothelial damage (syndecan-1), and liver PAI-1 mRNA expression. Rapid hemorrhage induced elevation of lactate and syndecan-1 levels and prolonged prothrombin time and activated partial thromboplastin time in the rapid group. In contrast, slow hemorrhage did not induce these changes. Hemorrhage speed had no effect on plasma tissue-type plasminogen activator and hematology. Plasma PAI-1 levels were significantly increased in the rapid-L group, while liver PAI-1 mRNA levels were increased in the slow group. This study shows changes in the circulatory and fibrinolysis systems, depending on the hemorrhage speed. Hemorrhage might promote production of PAI-1, while tissue hypoxia due to rapid hemorrhage might promote release of PAI-1.

Markers of Coagulation and Fibrinolysis Predicting the Outcome of Acute Ischemic Stroke Thrombolysis Treatment: A Review of the Literature

Intravenous administration of recombinant tissue plasminogen activator (rt-PA) has been proven to be safe and effective in the treatment of acute ischemic stroke. Little is known, however, why this treatment is less effective in some patients while in others life-threatening side-effects, e.g., symptomatic intracerebral hemorrhage might occur. Clinical failure of thrombolysis related to absent or partial recanalization or reocclusion as well as hemorrhagic complications of thrombolysis are possibly related to hemostatic events. Data on markers of coagulation and/or fibrinolysis in acute stroke patients are numerous and may provide indications regarding therapy outcomes. Better understanding of the hemostatic and fibrinolytic system during rt-PA therapy might be clinically useful and ultimately might lead to an improvement in the efficacy or safety of this treatment. Studies on thrombus composition retrieved from cerebral arteries may also advance our knowledge and provide a key to improve acute stroke therapy. Here we provide a comprehensive review on a wide range of factors and markers of coagulation and fibrinolysis that have been studied in the context of thrombolysis outcome in ischemic stroke patients. Moreover, a brief summary is given on the most recent research on thrombus composition having a potential influence on outcomes.

The role of plasminogen activators in stroke treatment: fibrinolysis and beyond

Although recent technical advances in thrombectomy have revolutionised acute stroke treatment, prevalence of disability and death related to stroke remain high. Therefore, plasminogen activators-eukaryotic, bacterial, or engineered forms that can promote fibrinolysis by converting plasminogen into active plasmin and facilitate clot breakdown-are still commonly used in the acute treatment of ischaemic stroke. Hence, plasminogen activators have become a crucial area for clinical investigation for their ability to recanalise occluded arteries in ischaemic stroke and to accelerate haematoma clearance in haemorrhagic stroke. However, inconsistent results, insufficient evidence of efficacy, or reports of side-effects in trial settings might reduce the use of plasminogen activators in clinical practice. Additionally, the mechanism of action for plasminogen activators could extend beyond the vessel lumen and involve plasminogen-independent processes, which would suggest that plasminogen activators have also non-fibrinolytic roles. Understanding the complex mechanisms of action of plasminogen activators can guide future directions for therapeutic interventions in patients with stroke.

Plasminogen Activator Inhibitor-1 Promotes Neutrophil Infiltration and Tissue Injury on Ischemia-Reperfusion

OBJECTIVE

Ischemia-reperfusion (I/R) injury significantly contributes to organ dysfunction and failure after myocardial infarction, stroke, and transplantation. In addition to its established role in the fibrinolytic system, plasminogen activator inhibitor-1 has recently been implicated in the pathogenesis of I/R injury. The underlying mechanisms remain largely obscure.

APPROACH AND RESULTS

Using different in vivo microscopy techniques as well as ex vivo analyses and in vitro assays, we identified that plasminogen activator inhibitor-1 rapidly accumulates on microvascular endothelial cells on I/R enabling this protease inhibitor to exhibit previously unrecognized functional properties by inducing an increase in the affinity of β2 integrins in intravascularly rolling neutrophils. These events are mediated through low-density lipoprotein receptor-related protein-1 and mitogen-activated protein kinase-dependent signaling pathways that initiate intravascular adherence of these immune cells to the microvascular endothelium. Subsequent to this process, extravasating neutrophils disrupt endothelial junctions and promote the postischemic microvascular leakage. Conversely, deficiency of plasminogen activator inhibitor-1 effectively reversed leukocyte infiltration, microvascular dysfunction, and tissue injury on experimental I/R without exhibiting side effects on microvascular hemostasis.

CONCLUSIONS

Our experimental data provide novel insights into the nonfibrinolytic properties of the fibrinolytic system and emphasize plasminogen activator inhibitor-1 as a promising target for the prevention and treatment of I/R injury.

A long-acting PAI-1 inhibitor reduces thrombus formation

Plasminogen activator inhibitor 1 (PAI-1) is the main inhibitor of tissue-type and urokinase-type plasminogen activators (t/uPA) and plays an important role in fibrinolysis. Inhibition of PAI-1 activity prevents thrombosis and accelerates fibrinolysis, indicating that PAI-1 inhibitors may be used as effective antithrombotic agents. We previously designed a PAI-1 inhibitor (PAItrap) which is a variant of inactivated urokinase protease domain. In the present study, we fused PAItrap with human serum albumin (HSA) to develop a long-acting PAI-1 inhibitor. Unfortunately, the fusion protein PAItrap-HSA lost some potency compared to PAItrap (33 nM vs 10 nM). Guided by computational method, we carried out further optimisation to enhance inhibitory potency for PAI-1. The new PAItrap, denominated PAItrap(H37R)-HSA, which was the H37R variant of PAItrap fused to HSA, gave a six-fold improvement of IC50 (5 nM) for human active PAI-1 compared to PAItrap-HSA, and showed much longer plasma half-life (200-fold) compared to PAItrap. We further demonstrated that the PAItrap(H37R)-HSA inhibited exogenous or endogenous PAI-1 to promote fibrinolysis in fibrin-clot lysis assay. PAItrap(H37R)-HSA inhibits murine PAI-1 with IC50 value of 12 nM, allowing the inhibitor to be evaluated in murine models. Using an intravital microscopy, we demonstrated that PAItrap(H37R)-HSA blocks thrombus formation and platelet accumulation in vivo in a laser-induced vascular injury mouse model. Additionally, mouse tail bleeding assay showed that PAItrap(H37R)-HSA did not affect the global haemostasis. These results suggest that PAItrap(H37R)-HSA have the potential benefit to prevent thrombosis and accelerates fibrinolysis.

Plasminogen activator inhibitor links obesity and thrombotic cerebrovascular diseases: The roles of PAI-1 and obesity on stroke

One of the global socioeconomic phenomena occurred during the last decades is the increased prevalence of obesity, with direct consequence on the risk of developing thrombotic disorders. As the physiological inhibitor of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) is well known for its role in fibrinolysis. More and more evidences have shown that PAI-1 involves in physiopathologic mechanisms of many diseases and metabolic disorder. Increased serum level of PAI-1 has been observed in obesity and it also contributes to the development of adipose tissue and then has effects on obesity. Meantime, obesity affects also the PAI-1 levels. These evidences indicate the complicated interaction between PAI-1 and obesity. Many clinic studies have confirmed that obesity relates to the stroke outcome although there are many contradictory results. Simultaneously, correlation is found between plasma PAI-1 and thrombotic cerebrovascular diseases. This article reviews contemporary knowledge regarding the complex interplay of obesity, PAI-1 and stroke.

Novel Thrombolytic Drug Based on Thrombin Cleavable Microplasminogen Coupled to a Single-Chain Antibody Specific for Activated GPIIb/IIIa

Background

Thrombolytic therapy for acute thrombosis is limited by life‐threatening side effects such as major bleeding and neurotoxicity. New treatment options with enhanced fibrinolytic potential are therefore required. Here, we report the development of a new thrombolytic molecule that exploits key features of thrombosis. We designed a recombinant microplasminogen modified to be activated by the prothrombotic serine‐protease thrombin (HtPlg), fused to an activation‐specific anti–glycoprotein IIb/IIIa single‐chain antibody (SCE5), thereby hijacking the coagulation system to initiate thrombolysis.

Methods and Results

The resulting fusion protein named SCE5‐HtPlg shows in vitro targeting towards the highly abundant activated form of the fibrinogen receptor glycoprotein IIb/IIIa expressed on activated human platelets. Following thrombin formation, SCE5‐HtPlg is activated to contain active microplasmin. We evaluate the effectiveness of our targeted thrombolytic construct in two models of thromboembolic disease. Administration of SCE5‐HtPlg (4 μg/g body weight) resulted in effective thrombolysis 20 minutes after injection in a ferric chloride–induced model of mesenteric thrombosis (48±3% versus 92±5% for saline control, P<0.01) and also reduced emboli formation in a model of pulmonary embolism (P<0.01 versus saline). Furthermore, at these effective therapeutic doses, the SCE5‐HtPlg did not prolong bleeding time compared with saline (P=0.99).

Conclusions

Our novel fusion molecule is a potent and effective treatment for thrombosis that enables in vivo thrombolysis without bleeding time prolongation. The activation of this construct by thrombin generated within the clot itself rather than by a plasminogen activator, which needs to be delivered systemically, provides a novel targeted approach to improve thrombolysis.

Stimulatory effect of an algal fucoidan on the release of vascular endothelial tissue-type plasminogen activator as a mechanism of fucoidan-mediated thrombolysis

Identifying a pharmacological means for increasing the production of tissue-type plasminogen activator (t-PA) is always desirable to cure impaired production of this enzyme. An algal fucoidan has been shown to exhibit both novel thrombolytic and synergistic stimulatory effects in a mouse thrombosis model. The plasma levels of active t-PA were measured in mouse arterial thrombus models that were treated with various fucoidans to investigate the mechanism of thrombolysis. The mean plasma level of active t-PA after the infusion of fucoidan was 2.136 ± 0.231 ng/ml for nonthrombolytic Fucus fucoidan and 3.917 ± 0.0.529 ng/ml for thrombolytic Undaria fucoidan, which resulted in a 1.56-2.29-fold increase compared with the healthy control group (1.706 ± 0.194 ng/ml) and the untreated thrombus group (2.506 ± 0.301 ng/ml) (P < 0.01). An algal fucoidan has demonstrated to exert a thrombolytic and stimulatory effect via the induction of t-PA release in a dose-dependent manner in an arterial thrombosis model.

What causes intracerebral bleeding after thrombolysis for acute ischaemic stroke? Recent insights into mechanisms and potential biomarkers

The overall population benefit of intravascular recombinant tissue plasminogen activator (rtPA) on functional outcome in ischaemic stroke is clear, but there are some treated patients who are harmed by early symptomatic intracranial haemorrhage (ICH). Although several clinical and radiological factors increase the risk of rtPA-related ICH, none of the currently available risk prediction tools are yet useful for practical clinical decision-making, probably reflecting our limited understanding of the underlying mechanisms. Finding new methods to identify patients at highest risk of rtPA-related ICH, or new measures to limit risk, are urgent challenges in acute stroke therapy research. In this article, we focus on the potential underlying mechanisms of rtPA-related ICH, highlight promising candidate risk biomarkers and suggest future research directions.

Innovative thrombolytic strategy using a heterodimer diabody against TAFI and PAI-1 in mouse models of thrombosis and stroke

Circulating thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor-1 (PAI-1) are causal factors for thrombolytic failure. Therefore, we evaluated an antibody-engineered bispecific inhibitor against TAFI and PAI-1 (heterodimer diabody, Db-TCK26D6x33H1F7) in several mouse models of thrombosis and stroke. Prophylactic administration of the diabody (0.8 mg/kg) in a thromboplastin-induced model of thromboembolism led to decreased lung fibrin deposition. In a model of cerebral ischemia and reperfusion, diabody administration (0.8 mg/kg, 1 hour postocclusion) led to a mitigated cerebral injury with a 2.3-fold reduced lesion and improved functional outcomes. In a mouse model of thrombin-induced middle cerebral artery occlusion, the efficacy of the diabody was compared to the standard thrombolytic treatment with recombinant tissue-type plasminogen activator (tPA). Early administration of diabody (0.8 mg/kg) caused a twofold decrease in brain lesion size, whereas that of tPA (10 mg/kg) had a much smaller effect. Delayed administration of diabody or tPA had no effect on lesion size, whereas the combined administration of diabody with tPA caused a 1.7-fold decrease in lesion size. In contrast to tPA, the diabody did not increase accumulative bleeding. In conclusion, administration of a bispecific inhibitor against TAFI and PAI-1 results in a prominent profibrinolytic effect in mice without increased bleeding.

Effects of a TAFI-inhibitor combined with a suboptimal dose of rtPA in a murine thromboembolic model of stroke

BACKGROUND

Since thrombolysis is the only approved intervention for ischemic stroke, improving its efficacy and safety is a therapeutic aim of considerable interest. The activated form of thrombin activatable fibrinolysis inhibitor (TAFI) has antifibrinolytic effects, and inhibition of TAFI might thus favor recanalization. The present study compared efficacy between TAFI inhibition alone and TAFI inhibition in combination with rtPA at a suboptimal dose, in a murine model of thromboembolic stroke.

METHODS

Focal ischemia was induced in mice by thrombin injection in the middle cerebral artery. Animals were placed within the magnet immediately after surgery for baseline MRI (H0). MRI examination comprised diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), and T2-weighted imaging (T2-WI). Animals were randomly assigned to 1 of 5 treatment groups: saline, rtPA 5 mg/kg (tPA(5): suboptimal or low dose), rtPA 10 mg/kg (tPA(10): standard dose), TAFI-I 100 mg/kg (TAFI-I), and rtPA 5 mg/kg + TAFI-I 100 mg/kg (tPA(5) + TAFI-I). Treatments were administered inside the magnet, via a catheter placed in the tail vein, using a power injector, as 10% bolus and 90% infusion over a period of 20 min. MRI examination was repeated at 3 h (H3) and 24 h (H24) after surgery. Therapeutic benefit was evaluated by: (1) improvement of reperfusion and (2) reduction in final lesion size. Microhemorrhages were assessed as black spots on T2-WI at H24. Animals were sacrificed after the last MR examination. The surgeon and all investigators were blinded to treatment allocation.

RESULTS

A total of 104 mice were operated on. Forty four of these were excluded from the study and 27 from the analysis, according to a priori defined criteria (no lesion or no mismatch), leading to the following distribution: saline (n = 6), tPA(5) (n = 8), tPA(10) (n = 7), TAFI-I (n = 7), and TAFI-I + tPA(5) (n = 5). Standard-dose rtPA treatment (tPA(10)) significantly improved lesion regression between H0 and H24 compared to saline (-57 ± 18% vs. -36 ± 21%, p = 0.03), which treatment with rtPA(5) or TAFI-I alone did not. On the other hand, combined treatment with tPA(5) + TAFI-I showed only a trend toward lesion regression (-49 ± 26%), similarly to treatment with tPA(10), but not significantly different from saline (p = 0.46). Nine animals showed microhemorrhage on T2-WI at H24. These animals were evenly distributed between groups.

CONCLUSIONS

The present study showed that the combination of TAFI-I with a suboptimal dose of rtPA is not as effective as the standard dose of rtPA, while TAFI inhibition alone is not effective at all. The thromboembolic model is of particular interest in assessing rtPA association to improve thrombolysis, especially when coupled with longitudinal MRI assessment.

Gene-drug interaction in stroke

Stroke is the third cause of mortality and one of most frequent causes of long-term neurological disability, as well as a complex disease that results from the interaction of environmental and genetic factors. The focus on genetics has produced a large number of studies with the objective of revealing the genetic basis of cerebrovascular diseases. Furthermore, pharmacogenetic research has investigated the relation between genetic variability and drug effectiveness/toxicity. This review will examine the implications of pharmacogenetics of stroke; data on antihypertensives, statins, antiplatelets, anticoagulants, and recombinant tissue plasminogen activator will be illustrated. Several polymorphisms have been studied and some have been associated with positive drug-gene interaction on stroke, but the superiority of the genotype-guided approach over the clinical approach has not been proved yet; for this reason, it is not routinely recommended.

Inflammatory and neuroendocrine biomarkers of prognosis after ischemic stroke

Stroke is the third leading cause of mortality in the USA and one of the leading causes of severe morbidity. It is important to provide stroke patients and physicians with the most accurate prognostic information to optimize care and allocation of healthcare resources. Reliable prognostic markers available during the initial phase after acute stroke may aid clinical decision-making. Several interesting candidate biomarkers have been studied to address prognostic questions; this article will focus on selected inflammatory and neuroendocrine markers. The utility of a biomarker is defined by its ability to improve clinical decision-making and add timely information beyond that readily available from clinical examination and routine imaging. This aim has not been completely achieved yet for any biomarkers, but promising data are available and further studies are ongoing.

Update on the Serum Biomarkers and Genetic Factors Associated with Safety and Efficacy of rt-PA Treatment in Acute Stroke Patients

An accurate understanding of the mechanisms underlying an individual's response to rt-PA treatment is critical to improve stroke patients' management. We thus reviewed the literature in order to identify biochemical and genetic factors that have been associated with safety and efficacy of rt-PA administration after stroke.

CD40-1C>T polymorphism (rs1883832) is associated with brain vessel reocclusion after fibrinolysis in ischemic stroke

AIMS

To find genetic predictors of reocclusion after successful fibrinolytic therapy during the acute phase of ischemic stroke.

PATIENTS & METHODS

This was a case-case prospective study analyzing 236 polymorphisms in a cohort of 222 patients treated with tissue plasminogen activator, from which 16 patients suffered a reocclusion event (7.2%). A predictive scale was generated using independent polymorphisms with a dominant/recessive model and tandem occlusion, weighted by their beta-coefficients in logistic regression.

RESULTS

Using a dominant/recessive model, the rs1800801 SNP from the MGP gene (odds ratio [OR]: 15.25; 95% CI: 2.23-104.46; adjusted p = 0.006) and the rs1883832 SNP from CD40 gene (OR: 0.077; 95% CI: 0.009-0.66; adjusted p = 0.019) were independently associated with reocclusion after logistic regression adjustment by clinical predictors. In an additive model, only the rs1883832 SNP (OR: 4.43; 95% CI: 1.62-12.15; adjusted p = 0.004) was related to reocclusion occurrence. The predictive model that was generated stratified the reocclusion risk from less than 1% to more than 70%. Reocclusions were associated with neurological worsening at 24 h (patients with reocclusion: 26.7%, versus patients without reocclusion: 4.9%; p = 0.002), as it was seen for MGP -7A>G (AA: 17.2% vs AG+GG: 4.5%; p = 0.027), but not for CD40 1C>T (CC: 4.5% vs CT+TT: 7.7%; p = 0.565). There was an association between CD40 -1C>T genotype and CD40 transcriptional activity in peripheral blood mononuclear cells (median expression values TT: 65.75%, CT: 70.80%, CC: 96.00%; p = 0.023). However, CD40 soluble fraction was not a useful biomarker of reocclusion status.

CONCLUSION

An association was found between MGP -7A>G and CD40 -1C>T polymorphisms, and reocclusion risk. The predictive scale that was generated permits the stratification of patients by their reocclusion risk with higher accuracy than clinical parameters alone.

Stroke pharmacogenomics

Circulatory disease accounts for fifteen million deaths each year, of which stroke accounts for four and a half million- with an estimated nine million stroke survivors annually. The overall incidence rate of stroke is 2 to 2.5 per thousand adults with an approximate prevalence of 5 per thousand and an estimated 5-year risk of stroke recurrence of 15 to 40 percent. Conventional risk factors for stroke include: increasing age, hypertension, diabetes mellitus, smoking, increased body mass index, ischemic heart disease, heart failure, atrial fibrillation and lack of physical activity. Age is the strongest risk factor for both ischemic and haemorrhagic stroke with its incidence doubling for each successive decade after the age of fifty-five years. However, there is a substantial portion of patients with significant cerebrovascular disease who do not have any of these stroke risk-factors, leading to the speculation that there are other factors that have not been identified yet So as to improve diagnosis and treatment strategies, as well as to reduce the related public health burden, it could be helpful to successfully identify its extremely complex genetic determinants (polygenic, multiple genes play a role). Pharmacogenetics is the field of pharmacology that deals with the influence of genetic variation on drug response by correlating gene expression and gene variants with the efficacy or toxicity of drugs. The principle drugs in stroke medicine are antithrombotics. The aim of this paper was to review the most commonly used drugs for stroke such as rtPA in the acute phase as well as antiplatelets and wafarin for secondary prophylaxis.

Pharmacogenetics in cardiovascular antithrombotic therapy

Thrombosis is the most important underlying mechanism of coronary artery disease and embolic stroke. Hence, antithrombotic therapy is widely used in these scenarios. However, not all patients achieve the same degree of benefit from antithrombotic agents, and a considerable number of treated patients will continue to experience a new thrombotic event. Such lack of clinical benefit may be related to a wide variability of responses to antithrombotic treatment among individuals (i.e., interindividual heterogeneity). Several factors have been identified in this interindividual heterogeneity in response to antithrombotic treatment. Pharmacogenetics has emerged as a field that identifies specific gene variants able to explain the variability in patient response to a given drug. Polymorphisms affecting the disposition, metabolism, transporters, or targets of a drug all can be implicated in the modification of an individual's antithrombotic drug response and therefore the safety and efficacy of the aforementioned drug. The present paper reviews the modulating role of different polymorphisms on individuals' responses to antithrombotic drugs commonly used in clinical practice.

Natural occurring polyphenols as template for drug design. Focus on serine proteases

Several major physio-pathological processes, including cancer, inflammatory states and thrombosis, are all strongly dependent upon the fine regulation of proteolytic enzyme activities, and dramatic are the consequences of unbalanced equilibria between enzymes and their cognate inhibitors. In this perspective, the discovery of small-molecule ligands able to modulate catalytic activities has a massive therapeutic potential and is a stimulating goal. Numerous recent experimental evidences revealed that proteolytic enzymes can be opportunely targeted, reporting on small ligands capable of binding to these biological macromolecules with drug-like potencies, and primarily with comparable (or even higher) efficiency with respect to their endogenous binding partner. In particular, natural occurring polyphenols and their derivatives recently disclosed these intriguing abilities, making them promising templates for drug design and development. In this review, we compared the inhibitory capacities of a set of monomeric polyphenols toward serine proteases activity, and finally summarized the data with an emphasis on the derivation of a pharmacophore model.

Do women benefit more from systemic thrombolysis in acute ischemic stroke? A Serbian experience with thrombolysis in ischemic stroke (SETIS) study

OBJECTIVE

The female sex is associated with increased stroke severity and relatively poor functional recovery. Several studies have demonstrated that women with stroke benefit more from intravenous thrombolysis compared with men, while others found the nullification of gender effect among women treated with recombinant tissue plasminogen activator (rtPA). The purpose of our study was to determine any gender differences in the efficacy and safety of systemic thrombolysis among patients with acute ischemic stroke in Serbia.

METHODS

Data were from the Serbian experience with intravenous thrombolysis in ischemic stroke (SETIS) study, a prospective, ongoing, multicenter, open, and observational study in Serbia of all patients who have received rtPA for acute ischemic stroke. We analyzed sex differences in the baseline characteristics, functional outcome and treatment complications.

RESULTS

Among 60 women and 96 men with stroke and treated with intravenous thrombolysis, we found that at day 90, no significant sex differences in excellent functional outcome (50.9% of women vs. 57.0% of men, p=0.5), favorable functional outcome (61.4% of women vs. 68.8% of men, p=0.38) or death (8.8% of women vs. 12.9% of men, p=0.60). These results were constant even after adjustments for age, severity of basal neurological deficit and onset to treatment time.

CONCLUSION

There were no sex differences in functional outcome at 90 days after the stroke among patients treated with IV rtPA. This finding might confirm that thrombolytic therapy nullifies usual sex differences in stroke outcome and suggests that women with stroke may benefit more from rtPA treatment.

Molecular biomarkers in stroke diagnosis and prognosis

Serum biomarkers related to the cascade of inflammatory, hemostatic, glial and neuronal perturbations have been identifed to diagnose and characterize intracerebral hemorrhage and cerebral ischemia. Interpretation of most markers is confounded by their latent rise, blood-brain barrier effects, the heterogeneity of etiologies and the wide range of normal values, limiting their application for early diagnosis, lesion size estimation and long-term outcome prediction. Certain hemostatic and inflammatory constituents have been found to predict response to thrombolysis and worsening due to infarct progression and secondary hemorrhage, offering a potential role for improved treatment selection and individualization of therapy. Biomarkers will become increasingly relevant for developing targets for neuroprotective therapies, monitoring response to treatment and as surrogate end points for treatment trials.

Mechanisms and markers for hemorrhagic transformation after stroke

Intracerebral hemorrhagic transformation is a multifactorial phenomenon in which ischemic brain tissue converts into a hemorrhagic lesion with blood vessel leakage. Hemorrhagic transformation can significantly contribute to additional brain injury after stroke. Especially threatening are the thrombolytic-induced hemorrhages after reperfusion therapy with tissue plasminogen activator (tPA), the only treatment available for ischemic stroke. In this context, it is important to understand its underlying mechanisms and identify early markers of hemorrhagic transformation, so that we can both search for new treatments as well as predict clinical outcomes in patients. In this review, we discuss the emerging mechanisms for hemorrhagic transformation after stroke, and briefly survey potential molecular, genetic, and neuroimaging markers that might be used for early detection of this challenging clinical problem.