Extension of ischemic therapeutic time window by a free radical scavenger, Edaravone, reperfused with tPA in rat brain

After Ischemic Stroke, Minocycline Promotes a Protective Response in Neurons via the RNA-Binding Protein HuR, with a Positive Impact on Motor Performance

Ischemic stroke is the most common cause of adult disability and one of the leading causes of death worldwide, with a serious socio-economic impact. In the present work, we used a new thromboembolic model, recently developed in our lab, to induce focal cerebral ischemic (FCI) stroke in rats without reperfusion. We analyzed selected proteins implicated in the inflammatory response (such as the RNA-binding protein HuR, TNFα, and HSP70) via immunohistochemistry and western blotting techniques. The main goal of the study was to evaluate the beneficial effects of a single administration of minocycline at a low dose (1 mg/kg intravenously administered 10 min after FCI) on the neurons localized in the penumbra area after an ischemic stroke. Furthermore, given the importance of understanding the crosstalk between molecular parameters and motor functions following FCI, motor tests were also performed, such as the Horizontal Runway Elevated test, CatWalk™ XT, and Grip Strength test. Our results indicate that a single administration of a low dose of minocycline increased the viability of neurons and reduced the neurodegeneration caused by ischemia, resulting in a significant reduction in the infarct volume. At the molecular level, minocycline resulted in a reduction in TNFα content coupled with an increase in the levels of both HSP70 and HuR proteins in the penumbra area. Considering that both HSP70 and TNF-α transcripts are targeted by HuR, the obtained results suggest that, following FCI, this RNA-binding protein promotes a protective response by shifting its binding towards HSP70 instead of TNF-α. Most importantly, motor tests showed that reduced inflammation in the brain damaged area after minocycline treatment directly translated into a better motor performance, which is a fundamental outcome when searching for new therapeutic options for clinical practice.

The Role of Pericytes in Ischemic Stroke: Fom Cellular Functions to Therapeutic Targets

Ischemic stroke (IS) is a cerebrovascular disease causing high rates of disability and fatality. In recent years, the concept of the neurovascular unit (NVU) has been accepted by an increasing number of researchers and is expected to become a new paradigm for exploring the pathogenesis and treatment of IS. NVUs are composed of neurons, endothelial cells, pericytes, astrocytes, microglia, and the extracellular matrix. As an important part of the NVU, pericytes provide support for other cellular components and perform a variety of functions, including participating in the maintenance of the normal physiological function of the blood–brain barrier, regulating blood flow, and playing a role in inflammation, angiogenesis, and neurogenesis. Therefore, treatment strategies targeting pericyte functions, regulating pericyte epigenetics, and transplanting pericytes warrant exploration. In this review, we describe the reactions of pericytes after IS, summarize the potential therapeutic targets and strategies targeting pericytes for IS, and provide new treatment ideas for ischemic stroke.

Neuroprotective effects of combination therapy of regional cold perfusion and hemoglobin-based oxygen carrier administration on rat transient cerebral ischemia

Regional cold perfusion and hemoglobin-based oxygen carrier administration both exert neuroprotective effects against cerebral ischemia reperfusion injury. We herein investigated whether the combination of these two therapies leads to stronger neuroprotective effects. Combination therapy was performed with the regional perfusion of cold HemoAct, a core-shell structured hemoglobin-albumin cluster, in a rat transient middle cerebral artery occlusion model. The effects of combination therapy, the intra-arterial administration of 10 °C HemoAct (10H) initiated at the onset of reperfusion, were compared with those of monotherapies, the intra-arterial administration of 10 °C saline (10S) and 37 °C HemoAct (37H), and an untreated control under the condition of 2-hour ischemia/24-hour reperfusion. The durability of therapeutic effects and the therapeutic time window of combination therapy were assessed based on comparisons with the 10H and control groups. Significantly better neurological findings and smaller infarct volumes were observed in the three treated (10S, 37H, and 10H) groups than in the control group. Among the 3 treated groups, only the 10H group showed significant improvements over the control group in the other items examined, including cerebral blood flow reduction, brain edema, and protein extravasation. The significant therapeutic effects of combination therapy on neurological disabilities and infarct volumes were confirmed at least until 7 days after reperfusion. Furthermore, combination therapy ameliorated neurological disabilities and hemorrhagic transformation in rats subjected to 4- and 5-hour ischemia/24-hour reperfusion. Since therapeutic effects may be expected until at least 5 h of complete ischemia and reperfusion, this combination therapy is a promising neuroprotective strategy against severe ischemic stroke.

Endothelial Targets in Stroke: Translating Animal Models to Human

Cerebral ischemia (stroke) induces injury to the cerebral endothelium that may contribute to parenchymal injury and worsen outcome. This review focuses on current preclinical studies examining how to prevent ischemia-induced endothelial dysfunction. It particularly focuses on targets at the endothelium itself. Those include endothelial tight junctions, transcytosis, endothelial cell death, and adhesion molecule expression. It also examines how such studies are being translated to the clinic, especially as adjunct therapies for preventing intracerebral hemorrhage during reperfusion of the ischemic brain. Identification of endothelial targets may prove valuable in a search for combination therapies that would specifically protect different cell types in ischemia.

Neuroprotective effects of SMTP-44D in mice stroke model in relation to neurovascular unit and trophic coupling

Stachybotrys microspora triprenyl phenol (SMTP)-44D has both anti-oxidative and anti-inflammatory activities, but its efficacy has not been proved in relation to the pathological changes of neurovascular unit (NVU) and neurovascular trophic coupling (NVTC) in ischemic stroke. Here, the present study was designed to assess the efficacies of SMTP-44D, moreover, compared with the standard neuroprotective reagent edaravone in ischemic brains. ICR mice were subjected to transient middle cerebral artery occlusion (tMCAO) for 60 min, SMTP-44D (10 mg/kg) or edaravone (3 mg/kg) was intravenously administrated through subclavian vein just after the reperfusion, and these mice were examined at 1, 3, and 7 d after reperfusion. Compared with the vehicle group, SMTP-44D treatment revealed obvious ameliorations in clinical scores and infarct volume, meanwhile, markedly suppressed the accumulations of 4-HNE, 8-OHdG, nitrotyrosine, RAGE, TNF-α, Iba-1, and cleaved caspase-3 after tMCAO. In addition, SMTP-44D significantly prevented the dissociation of NVU and improved the intensity of NAGO/BDNF and the number of BDNF/TrkB and BDNF/NeuN double positive cells. These effects of SMTP-44D in reducing oxidative and inflammatory stresses were similar to or stronger than those of edaravone. The present study demonstrated that SMTP-44D showed strong anti-oxidative, anti-inflammatory, and anti-apoptotic effects, moreover, the drug also significantly improved the NVU damage and NVTC in the ischemic brain.

Targeting oxidative stress for the treatment of ischemic stroke: Upstream and downstream therapeutic strategies

Excessive oxygen and its chemical derivatives, namely reactive oxygen species (ROS), produce oxidative stress that has been known to lead to cell injury in ischemic stroke. ROS can damage macromolecules such as proteins and lipids and leads to cell autophagy, apoptosis, and necrosis to the cells. This review describes studies on the generation of ROS, its role in the pathogenesis of ischemic stroke, and recent development in therapeutic strategies in reducing oxidative stress after ischemic stroke.

Recombinant Tissue Plasminogen Activator Induces Neurological Side Effects Independent on Thrombolysis in Mechanical Animal Models of Focal Cerebral Infarction: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Recombinant tissue plasminogen activator (rtPA) is the only effective drug approved by US FDA to treat ischemic stroke, and it contains pleiotropic effects besides thrombolysis. We performed a meta-analysis to clarify effect of tissue plasminogen activator (tPA) on cerebral infarction besides its thrombolysis property in mechanical animal stroke.

METHODS

Relevant studies were identified by two reviewers after searching online databases, including Pubmed, Embase, and ScienceDirect, from 1979 to 2016. We identified 6, 65, 17, 12, 16, 12 and 13 comparisons reporting effect of endogenous tPA on infarction volume and effects of rtPA on infarction volume, blood-brain barrier, brain edema, intracerebral hemorrhage, neurological function and mortality rate in all 47 included studies. Standardized mean differences for continuous measures and risk ratio for dichotomous measures were calculated to assess the effects of endogenous tPA and rtPA on cerebral infarction in animals. The quality of included studies was assessed using the Stroke Therapy Academic Industry Roundtable score. Subgroup analysis, meta-regression and sensitivity analysis were performed to explore sources of heterogeneity. Funnel plot, Trim and Fill method and Egger's test were obtained to detect publication bias.

RESULTS

We found that both endogenous tPA and rtPA had not enlarged infarction volume, or deteriorated neurological function. However, rtPA would disrupt blood-brain barrier, aggravate brain edema, induce intracerebral hemorrhage and increase mortality rate.

CONCLUSIONS

This meta-analysis reveals rtPA can lead to neurological side effects besides thrombolysis in mechanical animal stroke, which may account for clinical exacerbation for stroke patients that do not achieve vascular recanalization with rtPA.

Prophylactic Edaravone Prevents Transient Hypoxic-Ischemic Brain Injury: Implications for Perioperative Neuroprotection

BACKGROUND AND PURPOSE

Hypoperfusion-induced thrombosis is an important mechanism for postsurgery stroke and cognitive decline, but there are no perioperative neuroprotectants to date. This study investigated whether prophylactic application of Edaravone, a free radical scavenger already used in treating ischemic stroke in Japan, can prevent infarct and cognitive deficits in a murine model of transient cerebral hypoxia-ischemia.

METHODS

Adult male C57BL/6 mice were subjected to transient hypoxic-ischemic (tHI) insult that consists of 30-minute occlusion of the unilateral common carotid artery and exposure to 7.5% oxygen. Edaravone or saline was prophylactically applied to compare their effects on cortical oxygen saturation, blood flow, coagulation, oxidative stress, metabolites, and learning-memory using methods that include photoacoustic imaging, laser speckle contrast imaging, solid-state NMR, and Morris water maze. The effects on infarct size by Edaravone application at different time points after tHI were also compared.

RESULTS

Prophylactic administration of Edaravone (4.5 mg/kg×2, IP, 1 hour before and 1 hour after tHI) improved vascular reperfusion, oxygen saturation, and the maintenance of brain metabolites, reducing oxidative stress, thrombosis, white-matter injury, and learning impairment after tHI insult. Delayed Edaravone treatment after 3 h post-tHI became unable to reduce infarct size.

CONCLUSIONS

Acute application of Edaravone may be a useful strategy to prevent postsurgery stroke and cognitive impairment, especially in patients with severe carotid stenosis.

The free-radical scavenger edaravone accelerates thrombolysis with alteplase in an experimental thrombosis model

BACKGROUND AND PURPOSE

Reperfusion injury after thrombolytic therapy can have adverse neurologic effects. The free-radical scavenger edaravone is used in combination with the recombinant tissue plasminogen activator alteplase to treat acute ischemic stroke. However, basic investigations of this combination use remain inadequate. Here, we used an in vivo model to investigate the effects of edaravone on alteplase-induced thrombolysis.

METHODS

Thrombolysis was evaluated by using a He-Ne-laser-induced thrombosis model in rat mesenteric microvessels. Changes in thrombus volume were analyzed with the image analysis software Image-Pro Plus (Media Cybernetics, USA). There were three experimental groups (placebo, alteplase 0.6 mg/kg, alteplase 0.6 mg/kg + edaravone 10.5 mg/kg). Sequential changes (0 to 60 min) in thrombus volume were compared by using a relative optical density method that we had used previously.

RESULTS

In the placebo group, the thrombus volume at 60 min, reflecting the extent of thrombolysis, was 97.2% ± 5.7% of the initial value. In the alteplase group, thrombus volume decreased to 70.7% ± 4.1% (P<0.01) after 20 min and 14.2% ± 6.6% after 60 min. In the alteplase+edaravone group, thrombus volume decreased to 66.9% ± 7.2% (P<0.001) after 10 min and 10.9% ± 2.3% after 60 min.

CONCLUSIONS

These results support the hypothesis that edaravone accelerates thrombolysis by alteplase.

Phase II anti-inflammatory and immune-modulating drugs for acute ischaemic stroke

INTRODUCTION

Stroke is the second leading cause of death worldwide and the leading cause of adult neurological disability. Despite advances in stroke unit care, and increasing use of thrombolysis, there remains an urgent need for safe and effective treatments for acute ischaemic stroke. However, this is against a backdrop of multiple failures in translational drug development. Cerebral ischaemia initiates a complex cascade of immune and inflammatory pathways in the brain microvasculature and periphery, which contribute to the evolution of cerebral injury, resolution and repair. Targeting specific inflammatory or immune pathways, therefore, represents an attractive treatment strategy in acute ischaemic stroke. Although anti-inflammatory drugs have already failed in clinical trial development, several are currently at the Phase II developmental stage.

AREAS COVERED

The authors highlight several candidate drugs, which modulate a range of inflammatory and immune pathways, and have been investigated in pre-clinical and Phase II studies to date.

EXPERT OPINION

Drugs targeting inflammatory and immune pathways offer theoretical advantages including potentially longer therapeutic time windows and effects complementary to thrombolysis (ameliorating reperfusion injury). Fundamental changes in the approach to pre-clinical and clinical drug development are required to facilitate successful translation of promising candidate drugs into clinical practice.

Anti-oxidative nutrient-rich diet protects against acute ischemic brain damage in rats

We evaluated the neuroprotective effects of an anti-oxidative nutrient rich enteral diet (AO diet) that contained rich polyphenols (catechins and proanthocyanidins) and many other anti-oxidative ingredients. Wistar rats were treated with either vehicle, normal AO diet (containing 100kcal/100mL, catechin 38.75mg/100mL and proanthocyanidin 19mg/100mL, 1mL/day), or high AO diet (containing 10 times the polyphenols of the normal AO diet) for 14 days, and were subjected to 90min of transient middle cerebral artery occlusion. The AO diet improved motor function, reduced cerebral infarction volume, and decreased both peroxidative markers such as 4-hydroxynonenal, advanced glycation end products, 8-hydroxy-2-deoxyguanosine and inflammatory markers such as monocyte chemotactic protein-1, ionized calcium-binding adapter molecule-1, and tumor necrosis factor-α. Our study has shown that an AO diet has neuroprotective effects through both anti-oxidative and anti-inflammatory mechanisms, indicating that nutritional control with polyphenols could be useful for patients with acute ischemic stroke.

Pericyte protection by edaravone after tissue plasminogen activator treatment in rat cerebral ischemia

Pericytes play a pivotal role in contraction, mediating inflammation and regulation of blood flow in the brain. In this study, changes of pericytes in the neurovascular unit (NVU) were examined in relation to the effects of exogenous tissue plasminogen activator (tPA) and a free radical scavenger, edaravone. Immunohistochemistry and Western blot analyses showed that the overlap between platelet-derived growth factor receptor β-positive pericytes and N-acetylglucosamine oligomers (NAGO)-positive endothelial cells increased significantly at 4 days after 90 min of transient middle cerebral artery occlusion (tMCAO). The number of pericytes and the overlap with NAGO decreased with tPA but recovered with edaravone 4 days after tMCAO with proliferation. Thus, tPA treatment damaged pericytes, resulting in the detachment from astrocytes and a decrease in glial cell line-derived neurotrophic factor secretion. However, treatment with edaravone greatly improved tPA-induced damage to pericytes. The present study demonstrates that exogenous tPA strongly damages pericytes and destroys the integrity of the NVU, but edaravone treatment can greatly ameliorate such damage after acute cerebral ischemia in rats.

Synergy of combined tPA-edaravone therapy in experimental thrombotic stroke

Edaravone, a potent antioxidant, may improve thrombolytic therapy because it benefits ischemic stroke patients on its own and mitigates adverse effects of tissue plasminogen activator (tPA) in preclinical models. However, whether the combined tPA-edaravone therapy is more effective in reducing infarct size than singular treatment is uncertain. Here we investigated this issue using a transient hypoxia-ischemia (tHI)-induced thrombotic stroke model, in which adult C57BL/6 mice were subjected to reversible ligation of the unilateral common carotid artery plus inhalation of 7.5% oxygen for 30 min. While unilateral occlusion of the common carotid artery suppressed cerebral blood flow transiently, the addition of hypoxia triggered reperfusion deficits, endogenous thrombosis, and attenuated tPA activity, leading up to infarction. We compared the outcomes of vehicle-controls, edaravone treatment, tPA treatment at 0.5, 1, or 4 h post-tHI, and combined tPA-edaravone therapies with mortality rate and infarct size as the primary end-points. The best treatment was further compared with vehicle-controls in behavioral, biochemical, and diffusion tensor imaging (DTI) analyses. We found that application of tPA at 0.5 or 1 h – but not at 4 h post-tHI – significantly decreased infarct size and showed synergistic (p<0.05) or additive benefits with the adjuvant edaravone treatment, respectively. The acute tPA-edaravone treatment conferred >50% reduction of mortality, ∼80% decline in infarct size, and strong white-matter protection. It also improved vascular reperfusion and decreased oxidative stress, inflammatory cytokines, and matrix metalloproteinase activities. In conclusion, edaravone synergizes with acute tPA treatment in experimental thrombotic stroke, suggesting that clinical application of the combined tPA-edaravone therapy merits investigation.

Pre-treatment with the synthetic antioxidant T-butyl bisphenol protects cerebral tissues from experimental ischemia reperfusion injury

Treatments to inhibit or repair neuronal cell damage sustained during focal ischemia/reperfusion injury in stroke are largely unavailable. We demonstrate that dietary supplementation with the antioxidant di-tert-butyl-bisphenol (BP) before injury decreases infarction and vascular complications in experimental stroke in an animal model. We confirm that BP, a synthetic polyphenol with superior radical-scavenging activity than vitamin E, crosses the blood-brain barrier and accumulates in rat brain. Supplementation with BP did not affect blood pressure or endogenous vitamin E levels in plasma or cerebral tissue. Pre-treatment with BP significantly lowered lipid, protein and thiol oxidation and decreased infarct size in animals subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. This neuroprotective action was accompanied by down-regulation of hypoxia inducible factor-1α and glucose transporter-1 mRNA levels, maintenance of neuronal tissue ATP concentration and inhibition of pro-apoptotic factors that together enhanced cerebral tissue viability after injury. That pre-treatment with BP ameliorates oxidative damage and preserves cerebral tissue during focal ischemic insult indicates that oxidative stress plays at least some causal role in promoting tissue damage in experimental stroke. The data strongly suggest that inhibition of oxidative stress through BP scavenging free radicals in vivo contributes significantly to neuroprotection. We demonstrate that pre-treatment with ditert-butyl bisphenol(Di-t-Bu-BP) inhibits lipid, protein, and total thiol oxidation and decreases caspase activation and infarct size in rats subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. These data suggest that inhibition of oxidative stress contributes significantly to neuroprotection.

Protective effect of telmisartan against progressive oxidative brain damage and synuclein phosphorylation in stroke-resistant spontaneously hypertensive rats

Previously, we reported that reactive oxygen species and signaling molecules of angiotensin II produced lipid peroxides, degenerated proteins, and injured DNA after cerebral ischemia in normotensive Wistar rats. Here, we investigated the long-term effect of the angiotensin II type I receptor blocker telmisartan on oxidative stress and hyperphosphorylated α-synuclein accumulation in stroke-resistant spontaneously hypertensive rats (SHR-SR). At the age of 3 months, SHR-SR were divided into 3 treatment groups: SHR-SR vehicle (SHR/Ve), SHR-SR low-dose telmisartan (.3 mg/kg/day) (SHR/low), and SHR-SR high-dose telmisartan (3 mg/kg/day) (SHR/high). Immunohistologic analyses were conducted in these groups and Wistar rats at the age of 6, 12, and 18 months. The SHR/Ve group demonstrated more progressive increase in advanced glycation end product (AGE)-, 4-hydroxy-2-nonenal (4-HNE)-, and phosphorylated α-synuclein (pSyn)-positive cells in the cerebral cortex and hippocampus compared with the Wistar group at 18 months. These expressions were reduced in the SHR/low group even without lowering blood pressure (BP), and expressions were dramatically suppressed in the SHR/high group with lowering of BP. These data suggest that persistent hypertension in SHR-SR strongly potentiate the markers of oxidative damage (AGEs and 4-HNE) and abnormal accumulation of pSyn, which were greatly suppressed by telmisartan in a dose-dependent manner without and with lowering of BP.

Edaravone Improves Functional and Structural Outcomes in Animal Models of Focal Cerebral Ischemia: A Systematic Review

Edaravone has been used in patients with acute ischemic stroke in Japan for over 10 years but does not have marketing authorization in Europe or America. Either patients in Europe and America are not receiving an effective treatment, or those in Asia are being given a treatment which is not effective. Finding out which of these is true will require further clinical trials, and a better understanding of its efficacy in animal models may help inform the design of those trials so that it might be tested under conditions where there is the greatest prospect of success. We systematically reviewed the efficacy of edaravone in animal models of focal ischemia and summarized data using weighted mean difference DerSimonian and Laird random-effects modeling. We used stratified meta-analysis and metaregression to assess the influence of study design and methodological quality. We identified 49 experiments describing outcome in 814 animals; 30 experiments (519 animals) reported functional and 35 experiments (503 animals) reported structural outcome. Edaravone improved functional and structural outcome by 30.3% (95% confidence interval 23.4–37.2%) and 25.5% (95% confidence interval, 21.1–29.9%), respectively. For functional outcome, there was an inverse relationship between study quality and effect size ( P < 0.0017). Effect sizes were larger in studies where randomization or blinded assessment was not reported. There was no evidence of publication bias. Edaravone is a promising treatment for stroke. However, because of the methodological weakness in current animal studies, no sufficient preclinical evidence is available to optimize the study design of clinical trials. Higher quality animal studies are expected to inform further clinical study.

Edaravone alleviates hypoxia-acidosis/reoxygenation-induced neuronal injury by activating ERK1/2

Edaravone, a free radical scavenger, is the first clinical drug of neuroprotection for ischemic stroke patients in the world, and has been shown to be an effective agent to alleviate cerebral ischemic injury. It has been established that acidosis is a common feature of cerebral ischemia and underlies the pathogenesis of ischemic stroke. In the present study, we investigated the role of edaravone in hypoxia-acidosis/reoxygenation (H-A/R)-induced neuronal injury that is partially mediated by the activation of acid-sensing ion channels (ASICs). Here, we observed that pretreatment of cultured neurons with edaravone largely reduced LDH release induced by acidosis or H-A/R. We also found that edaravone exhibited its neuroprotective roles by enhancing brain-derived neurotrophic factor (BDNF) and Bcl-2 expression, suppressing caspase-3 activity and promoting extracellular signal-regulated kinase1/2 (ERK1/2) activation. Furthermore, the addition of MEK (mitogen-activated protein kinase/ERK kinase) antagonists PD98059 and U0126 nearly abolished the beneficial effects of edaravone. Similarly, ASICs blockade produced the protective effects comparable to edaravone administration. These results indicate that edaravone is capable of attenuating H-A/R-mediated neurotoxicity at least partially through activating ERK1/2.

Intravenous thrombolysis with neuroprotective therapy by edaravone for ischemic stroke patients older than 80 years of age

BACKGROUND

Alteplase, a recombinant tissue plasminogen activator (tPA), was approved for patients with acute ischemic stroke within 3 hours of stroke onset in Japan in October 2005 at a dose of 0.6 mg/kg. The aim of this study was to assess the safety and efficacy of alteplase in elderly patients in Japan.

METHODS

One hundred twenty-nine consecutive patients who were admitted to our 5 hospital groups and who received intravenous tPA within 3 hours of stroke onset between January 2010 and December 2011 were divided into 2 groups by age (<80 years of age [younger group] and >80 years of age [older group]) and by treatment with or without edaravone. Clinical backgrounds and outcomes were investigated.

RESULTS

The National Institutes of Health Stroke Scale score on admission was not different in both groups, but the National Institutes of Health Stroke Scale scores 7 days after stroke onset were significantly higher in the older group (score 8; P < .05) than in the younger group (score 4), and the ratio of patients with a modified Rankin Scale score of 4 to 6 was significantly greater in the older group (41.7%; P < .05) than in the younger group (22.2%). However, there was no difference in asymptomatic and symptomatic intracerebral hemorrhage rates between the younger and older groups (asymptomatic 20.2% v 18.8%; symptomatic 2.6% v 2.1%). Patients with edaravone showed a higher recanalization rate (61.9%; P < .01) and a better modified Rankin Scale score at 3 months poststroke (P < .01) than the nonedaravone group.

CONCLUSIONS

These data suggest that intravenous alteplase (0.6 mg/kg) within 3 hours of stroke onset was safe and effective, even for very old patients (≥ 80 years of age), but resulted in poor outcomes relating not to tPA but to aging. In addition, edaravone may be a good partner for combination therapy with tPA to enhance recanalization and reduce hemorrhagic transformation.

Does inhibiting Sur1 complement rt-PA in cerebral ischemia?

Hemorrhagic transformation (HT) associated with recombinant tissue plasminogen activator (rt-PA) complicates and limits its use in stroke. Here, we provide a focused review on the involvement of matrix metalloproteinase 9 (MMP-9) in rt-PA-associated HT in cerebral ischemia, and we review emerging evidence that the selective inhibitor of the sulfonylurea receptor 1 (Sur1), glibenclamide (U.S. adopted name, glyburide), may provide protection against rt-PA-associated HT in cerebral ischemia. Glyburide inhibits activation of MMP-9, ameliorates edema formation, swelling, and symptomatic hemorrhagic transformation, and improves preclinical outcomes in several clinically relevant models of stroke, both without and with rt-PA treatment. A retrospective clinical study comparing outcomes in diabetic patients with stroke treated with rt-PA showed that those who were previously on and were maintained on a sulfonylurea fared significantly better than those whose diabetes was managed without sulfonylureas. Inhibition of Sur1 with injectable glyburide holds promise for ameliorating rt-PA-associated HT in stroke.

Edaravone (Radicut), a free radical scavenger, is a potentially useful addition to thrombolytic therapy in patients with acute ischemic stroke

Acute ischemic stroke (AIS) is a major cause of morbidity and mortality in the aging population worldwide. Alteplase, a recombinant tissue plasminogen activator, is the only Food and Drug Administration-approved thrombolytic agent for the treatment of AIS. Only 2-5% of patients with stroke receive thrombolytic treatment, mainly due to delay in reaching the hospital. Edaravone is a free radical scavenger marketed in Japan to treat patients with AIS, who present within 24 h of the onset of symptoms. When used in combination with alteplase, edaravone may have three useful effects: enhancement of early recanalization, inhibition of alteplase-induced hemorrhagic transformation and extension of the therapeutic time window for alteplase. This is the first review of the literature evaluating the clinical efficacy of edaravone, aiming to clarify whether edaravone should be further evaluated for clinical use worldwide. This review covers both clinical and experimental studies conducted between 1994 and 2012. Edaravone is a potentially useful neurovascular protective agent, used in combination with thrombolytic agents to treat >15 million patients devastated by stroke worldwide annually. Additional clinical studies are necessary to verify the efficacy of edaravone when used in combination with a thrombolytic agent.

A Rho kinase (ROCK) inhibitor, fasudil, prevents matrix metalloproteinase-9-related hemorrhagic transformation in mice treated with tissue plasminogen activator

Thrombolysis with tissue plasminogen activator (tPA) is the only FDA-approved therapy for acute ischemic stroke. However, hemorrhagic transformation, neurotoxicity, and a short treatment time window comprise major limitations for thrombolytic therapy. The purpose of the present study was to investigate whether fasudil, a Rho kinase (ROCK) inhibitor, would prevent tPA-associated hemorrhagic transformation and extend the reperfusion window in an experimental stroke model in mice. Mice subjected to 6-h middle cerebral artery occlusion were treated with delayed tPA alone, with combined tPA plus fasudil, or with a vehicle. We used histological and neurobehavioral measures to assess the effects of the treatment at 18 h and 7 days after the reperfusion. To investigate the mechanism of fasudil's beneficial effects further, we also performed an in vitro study with tPA and fasudil in human brain microvascular endothelial cells. Combination therapy with tPA plus fasudil prevented the development of hemorrhagic transformation, but did not reduce the infarct volumes. These changes significantly reduced mortality and increased locomotor activity at 7 days after the reperfusion. Furthermore, the administration of both drugs prevented injury to the human brain endothelial cells via the reduction of matrix metalloproteinase-9 (MMP-9) activity. These findings indicate that fasudil prevents the hemorrhagic transformation induced by focal cerebral ischemia in mice treated with tPA, at least in part, by inhibiting the increased activity of MMP-9 in endothelial cells.

The Relation of Urinary 8-OHdG, A Marker of Oxidative Stress to DNA, and Clinical Outcomes for Ischemic Stroke

Background:

Oxidative stress/free radical generation after ischemic stroke contributes to neuronal cell injury. We evaluated the utility of an oxidative stress marker, urinary 8-hydroxy-2-deoxyguanosine (8-OHdG), to demonstrate an association between the changes of 8-OHdG and outcomes after acute ischemic stroke.

Methods:

We enrolled 44 patients (26 males and 18 females) who visited our hospital due to acute ischemic stroke. Urine was collected on admission and on Days 7, and 8-OHdG was measured by ELISA. The relationships between 8-OHdG levels, stroke subtypes, and clinical outcomes based on the NIHSS and modified Rankin Scale (mRS) upon discharge was evaluated.

Results:

In the overall cohort, the mean urinary level of 8-OHdG on Day 7 was increased than that on Day 0. The 8-OHdG levels on Day 0 were not different between patients with poor and good outcomes. However, an increasing rate from Day 0 to 7 (Δ 8-OHdG) in stroke patients with a poor outcome(mRS ≥3) was significantly higher than those with a good outcome (mRS ≤2) (2.54 vs 39.44, p = 0.004).

Conclusions:

The biochemical changes related to 8-OHdG and oxidative stress may be considered a marker of ischemic brain injury and clinical outcome of ischemic stroke.

Modifying neurorepair and neuroregenerative factors with tPA and edaravone after transient middle cerebral artery occlusion in rat brain

Changes in expression of neurorepair and neuroregenerative factors were examined after transient cerebral ischemia in relation to the effects of tissue plasminogen activator (tPA) and the free radical scavenger edaravone. Physiological saline or edaravone was injected twice during 90 min of transient middle cerebral artery occlusion (tMCAO) in rats, followed by the same saline or tPA at reperfusion. Sizes of the infarct and protein factors relating to neurorepair and neuroregeneration were examined at 4d after tMCAO. The protein factors examined were: a chondroitin sulfate proteoglycan neurocan, semaphorin type 3A (Sema3A), a myelin-associated glycoprotein receptor (Nogo receptor, Nogo-R), a synaptic regenerative factor (growth associated protein-43, GAP43), and a chemotropic factor netrin receptor (deleted in colorectal cancer, DCC). Two groups treated by edaravone only or edaravone plus tPA showed a reduction in infarct volume compared to the two groups treated by vehicle only or vehicle plus tPA. Immunohistochemistry and western blot analyses indicated that protein expression of neurocan, Sema3A, Nogo-R, GAP43, and DCC was decreased with tPA, but recovered with edaravone. Additive edaravone prevented the reductions of these five proteins induced by tPA. The present study demonstrates for the first time that exogenous tPA reduced protein factors involved in inhibiting and promoting axonal growth, but that edaravone ameliorated such damage in brain repair after acute ischemia.

[Therapeutic time window for ischemic stroke]

Neuroprotection is essential for therapy in acute stage of stroke. Both neurotrophic factors (NTFs) and free radical scavenger can be such neuroprotective reagents with inhibiting death signals and potentiating survival signals under cerebral ischemia. Edaravone, a free radical scavenger, is the first clinical drug for neuroprotection in the world which has been used from 2001 in most ischemic stroke patients in Japan. Edaravone scavenges hydroxyl radicals both in hydrophilic and hydrophobic conditions, and is especially useful in thrombolytic therapy with tissue plasminogen activator (tPA). Combination therapy of Edaravone with tPA greatly increased survival of stroke animals, reduced infarct size, and inhibited molecular markers of oxidative damage in lipid, protein and DNA. Use of Edaravone greatly reduced hemorrhagic transformation accompanied by tPA treatment, and may also extend therapeutic time window with tPA therapy for more than 3 hr in human stroke patients.

[Future neuroprotective strategies in the post-thrombolysis era--neurovascular unit protection and vascular endothelial protection]

From an appearance of recombinant tissue plasminogen activator (rt-PA) in the clinical therapy on 2005 in Japan, the therapeutic strategy of ischemic stroke therapy is now changing dramatically. Many experimental data from animal stroke and clinical trials of neuroprotective agents failed to clinical useful therapeutic strategy. A free radical scavenger, edaravone is the first clinical drug for neuroprotection in the world which has been used in almost all ischemic stroke patients in Japan from 2001. Now, it is especially useful in thrombolytic therapy with rtPA, whereas we still need the newly more effective neuroprotective drugs which can be applied to many ischemic stroke patients. Therefore, we review and describe the future neuroprotective strategies in the post-thrombolysis era.

17β-estradiol attenuates breakdown of blood-brain barrier and hemorrhagic transformation induced by tissue plasminogen activator in cerebral ischemia

Tissue plasminogen activator (tPA) remains the only approved thrombolytic agent for the early treatment of ischemic stroke. However, treatment with tPA may lead to disruption of the blood-brain barrier and hemorrhagic transformation. 17β-estradiol (E2) has demonstrated efficacy in reduction of infarct volume in ischemic stroke models. The effects of acute administration of E2 on permeability of the blood-brain barrier and its ability to prevent hemorrhagic transformation in ischemic rats treated with tPA have not previously been studied. Here, we show that neurological deficits, brain water content, and Evan's blue extravasation were increased in ovariectomized female Wistar rats treated with tPA and attenuated in rats receiving E2+tPA. We also show that intracerebral hemoglobin and matrix metalloproteinase-9 activity were elevated with tPA treatment, and these increases were reduced by E2 treatment. Taken together, these data demonstrate that acute administration of E2 is capable of ameliorating some of the adverse effects of tPA administration, including the increase of matrix metalloproteinase-9 activity, blood-brain barrier permeability, and hemorrhagic transformation. These findings suggest a potential role for estrogen in thrombolytic treatment for ischemic stroke.

Striatal neuroprotection from neonatal hypoxia-ischemia in piglets by antioxidant treatment with EUK-134 or edaravone

Striatal neurons are highly vulnerable to hypoxia-ischemia (HI) in term newborns. In a piglet model of HI, striatal neurons develop oxidative stress and organelle disruption by 3-6 h of recovery and ischemic cytopathology over 6-24 h of recovery. We tested the hypothesis that early treatment with the antioxidants EUK-134 (a manganese-salen derivative that acts as a scavenger of superoxide, hydrogen peroxide, nitric oxide or NO and peroxynitrite) or edaravone (MCI-186, a scavenger of hydroxyl radical and NO) protects striatal neurons from HI. Anesthetized newborn piglets were subjected to 40 min of hypoxia and 7 min of airway occlusion. At 30 min after resuscitation, the piglets received vehicle, EUK-134 or edaravone. Drug treatment did not affect arterial blood pressure, blood gases, blood glucose or rectal temperature. At 4 days of recovery, the density of viable neurons in the putamen of vehicle-treated piglets was 12 ± 6% (±SD) of sham-operated control density. Treatment with EUK-134 increased viability to 41 ± 17%, and treatment with edaravone increased viability to 39 ± 19%. In the caudate nucleus, neuronal viability was increased from 54 ± 11% in the vehicle group to 78 ± 15% in the EUK-134 group and to 73 ± 13% in the edaravone group. Antioxidant drug treatment accelerated recovery from neurologic deficits and decreased oxidative and nitrative damage to nucleic acids. Treatment with EUK-134 reduced the HI-induced formation of protein carbonyl groups and tyrosine nitration at 3 h of recovery. We conclude that systemic administration of antioxidant agents by 30 min after resuscitation from HI can reduce oxidative stress and salvage neurons in the highly vulnerable striatum in a large-animal model of neonatal HI. Therefore, oxidative stress is an important mechanism for this injury, and antioxidant therapy is a rational, mechanism-based approach to neuroprotection in the newborn brain.

Improved brain MRI indices in the acute brain stem infarct sites treated with hydroxyl radical scavengers, Edaravone and hydrogen, as compared to Edaravone alone. A non-controlled study

BACKGROUND

In acute stage of cerebral infarction, MRI indices (rDWI & rADC) deteriorate during the first 3-7 days after the ictus and then gradually normalize in approximately 10 days (pseudonormalization time), although the tissue is already infarcted. Since effective treatments improve these indices significantly and in less than the natural pseudonormalization time, a combined analysis of these changes provides an opportunity for objective evaluation on the effectiveness of various treatments for cerebral infarction. Hydroxyl radicals are highly destructive to the tissue and aggravate cerebral infarction. We treated brainstem infarction patients in acute stage with hydroxyl radical scavengers (Edaravone and hydrogen) by intravenous administration and evaluated the effects of the treatment by a serial observation and analysis of these MRI indices. The effects of the treatment were evaluated and compared in two groups, an Edaravone alone group and a combined group with Edaravone and hydrogen, in order to assess beneficial effects of addition of hydrogen.

METHODS

The patients were divided in Edaravone only group (E group. 26 patients) and combined treatment group with Edaravone and hydrogen enriched saline (EH group. 8 patients). The extent of the initial hump of rDWI, the initial dip of rADC and pseudo-normalization time were determined in each patient serially and averages of these data were compared in these two groups and also with the natural course in the literatures.

RESULTS

The initial hump of rDWI reached 2.0 in the E group which was better than 2.5 of the natural course but was not as good as 1.5 of the EH group. The initial dip of rADC was 0.6 in the E group which was close to the natural course but worse than 0.8 of the EH group. Pseudonormalization time of rDWI and rADC was 9 days only in EH group but longer in other groups. Addition of hydrogen caused no side effects.

CONCLUSIONS

Administration of hydroxyl radical scavengers in acute stage of brainstem infarction improved MRI indices against the natural course. The effects were more obvious and significant in the EH group. These findings may imply the need for more frequent daily administration of hydroxyl scavenger, or possible additional hydrogen effects on scavenger mechanisms.

Effects of edaravone on a rat model of punch-drunk syndrome

Punch-drunk syndrome (PDS) refers to a pathological condition in which higher brain dysfunction occurs in a delayed fashion in boxers who have suffered repeated blows to the head. However, the underlying mechanisms remain unknown. This study attempted to elucidate the mechanism of higher brain dysfunction observed following skull vibration in two experiments involving a rat model of PDS. Experiment 1 evaluated the effects of edaravone on histological changes in the rat brain tissue after skull vibration (frequency 20 Hz, amplitude 4 mm, duration 60 minutes). The amount of free radicals formed in response to skull vibration was very small, and edaravone administration reduced the number of glial fibrillary acidic protein and advanced glycation end product-positive cells. Experiment 2 examined the time course of change in learning ability following skull vibration in Tokai High Avoider rats. The learning ability of individual rats was evaluated by the Sidman-type electric shock avoidance test 5 days after the last session of skull vibration or final anesthesia and once a month for 9 consecutive months. Delayed learning disability was not observed in rats administered edaravone immediately after skull vibration. These results suggest that free radical-induced astrocyte activation and subsequent glial scar formation contribute to the occurrence of delayed learning disabilities. Edaravone administration after skull vibration suppressed glial scar formation, thereby inhibiting the occurrence of delayed learning disabilities.

In vivo optical imaging for evaluating the efficacy of edaravone after transient cerebral ischemia in mice

Detection and protection of apoptosis, autophagy and neurovascular unit (NVU) are essentially important in understanding and treatment for ischemic stroke patients. In this study, we have conducted an in vivo optical imaging for detecting apoptosis and activation of matrix metalloproteinases (MMPs), then evaluated the protective effect of 2 package types of free radical scavenger edaravone (A and B) on apoptosis, autophagy and NVU in mice after transient middle cerebral artery occlusion (tMCAO). As compared to vehicle treatment, edaravones A and B showed a significant improvement of clinical scores and infarct size at 48 h after 90 min of tMCAO with great reductions of in vivo fluorescent signal for MMPs and early apoptotic annexin V activations. Ex vivo imaging of MMPSense 680 or annexin V-Cy5.5 showed a fluorescent signal, while which was remarkably different between vehicle and edaravone groups, and colocalized with antibody for MMP-9 or annexin V. Edaravone A and B ameliorated the apoptotic neuronal cell death in immunohistochemistry, and activations of MMP-9 and aquaporin 4 with reducing autophagic activations of microtubule-associated protein 1 light chain 3 (LC3) in Western blot. In this study, edaravone in both packages showed a similar strong neuroprotection after cerebral ischemia, which was confirmed with in vivo and ex vivo optical imagings for MMPs and annexin V as well as reducing cerebral infarct, inhibiting apoptotic/autophagic mechanisms, and protecting a part of neurovascular unit.

Edaravone, a free radical scavenger, promotes engraftment of intraportally transplanted islet cells

OBJECTIVES

Pancreatic islet transplantation requires multiple transplants to achieve insulin independence. Only one third of the islet mass is stably engrafted; one of the causes of which is ascribed to oxidative stress. We confirmed the hypothesis that administration of edaravone, a free radical scavenger, in the early posttransplantation period promotes islet cell engraftment.

METHODS

Islet isograft from a single donor was intraportally transplanted into streptozotocin-diabetic F344 rats, and intravenous edaravone (3 mg/kg) was administered immediately and 24 hours after the transplantation. Plasma glucose concentrations were monitored for 28 days. Serum insulin levels were obtained on the second week. Morphologic studies were performed on insulin-immunostained and TUNEL-stained sections of the recipient liver.

RESULTS

In the edaravone-treated group, hyperglycemia was ameliorated, and 50% of rats achieved normoglycemia (<200 mg/dL). All rats in the control group remained hyperglycemic (>400 mg/dL). Insulin secretion of the edaravone-treated group was superior to the controls. Morphologically, the number and size of the islet β cells of the edaravone-treated group were larger than those of the controls. The number of TUNEL-positive cells in each islet of the edaravone-treated group were fewer than those of the controls.

CONCLUSIONS

In streptozotocin-diabetic rats, edaravone administration in the early posttransplantation period promotes engraftment of intraportally transplanted islet cells.

Phosphodiesterase-III inhibitor prevents hemorrhagic transformation induced by focal cerebral ischemia in mice treated with tPA

The purpose of the present study was to investigate whether cilostazol, a phosphodiesterase-III inhibitor and antiplatelet drug, would prevent tPA-associated hemorrhagic transformation. Mice subjected to 6-h middle cerebral artery occlusion were treated with delayed tPA alone at 6 h, with combined tPA plus cilostazol at 6 h, or with vehicle at 6 h. We used multiple imaging (electron microscopy, spectroscopy), histological and neurobehavioral measures to assess the effects of the treatment at 18 h and 7 days after the reperfusion. To further investigate the mechanism of cilostazol to beneficial effect, we also performed an in vitro study with tPA and a phosphodiesterase-III inhibitor in human brain microvascular endothelial cells, pericytes, and astrocytes. Combination therapy with tPA plus cilostazol prevented development of hemorrhagic transformation, reduced brain edema, prevented endothelial injury via reduction MMP-9 activity, and prevented the blood-brain barrier opening by inhibiting decreased claudin-5 expression. These changes significantly reduced the morbidity and mortality at 18 h and 7 days after the reperfusion. Also, the administration of both drugs prevented injury to brain human endothelial cells and human brain pericytes. The present study indicates that a phosphodiesterase-III inhibitor prevents the hemorrhagic transformation induced by focal cerebral ischemia in mice treated with tPA.

The contribution of L-arginine to the neurotoxicity of recombinant tissue plasminogen activator following cerebral ischemia: a review of rtPA neurotoxicity

Alteplase is the only drug licensed for acute ischemic stroke, and in this formulation, the thrombolytic agent recombinant tissue plasminogen activator (rtPA) is stabilized in a solution of L-arginine. Improved functional outcomes after alteplase administration have been shown in clinical trials, along with improved histological and behavioral measures in experimental models of embolic stroke. However, in animal models of mechanically induced ischemia, alteplase can exacerbate ischemic damage. We have systematically reviewed the literature of both rtPA and L-arginine administration in mechanical focal ischemia. The rtPA worsens ischemic damage under certain conditions, whereas L-arginine can have both beneficial and deleterious effects dependent on the time of administration. The interaction between rtPA and L-arginine may be leading to the production of nitric oxide, which can cause direct neurotoxicity, altered cerebral blood flow, and disruption of the neurovascular unit. We suggest that alternative formulations of rtPA, in the absence of L-arginine, would provide new insight into rtPA neurotoxicity, and have the potential to offer more efficacious thrombolytic therapy for ischemic stroke patients.

Vascular protection and restorative therapy in ischemic stroke

Possible strategies for treating stroke include: 1) thrombolytic therapy with tissue plasminogen activator (tPA): restoring cerebral blood flow in the acute phase of ischemic stroke but sometimes causing hemorrhagic transformation (HT); 2) stem cell therapy: the repair of disrupted neuronal networks with newly born neurons in the chronic phase of ischemic stroke. Firstly, we estimated the vascular protective effect of a free radical scavenger, edaravone, in the tPA-treated rat model of middle cerebral artery occlusion. Edaravone prevented dramatically decreased the hemorrhagic transformation and improved the neurologic score and survival rate of tPA-treated rats. Secondly, we attempted to restore brain tissue using a novel biomaterial, polydimethysiloxane-tetraethoxysilane (PDMS-TEOS) hybrid with or without vascular endothelial growth factor (VEGF), and we could show that implantation of a PDMS-TEOS scaffold with VEGF might be effective for treating old brain infarction or trauma. In the future, we will combine these strategies to develop more effective therapies for treatment of strokes.

Edaravone: a new therapeutic approach for the treatment of acute stroke

Acute stroke, including acute ischemic stroke (AIS) and acute hemorrhagic stroke, (AHS) is a common medical problem with particular relevance to the demographic changes in industrialized societies. In recent years, treatments for AIS have emerged, including thrombolysis with tissue plasminogen activator (t-PA). Although t-PA is the most effective currently available therapy, it is limited by a narrow therapeutic time window and side effects, and only 3% of all AIS patients receive thrombolysis. Edaravone was originally developed as a potent free radical scavenger and, since 2001, has been widely used to treat AIS in Japan. It was shown that edaravone extended the narrow therapeutic time window of t-PA in rats. The therapeutic time window is very important for the treatment of AIS, and early edaravone treatment is more effective. Thus, more AIS patients might be rescued by administering edaravone with t-PA. Meanwhile, edaravone attenuates AHS-induced brain edema, neurologic deficits and oxidative injury in rats. Although edaravone treatment is currently only indicated for AIS, it does offer neuroprotective effects against AHS in rats. Therefore, we hypothesize that early administration of edaravone can rescue AHS patients as well as AIS patients. Taken together, our findings suggest that edaravone should be immediately administered on suspicion of acute stroke, including AIS and AHS.

A novel embolic model of cerebral infarction and evaluation of Stachybotrys microspora triprenyl phenol-7 (SMTP-7), a novel fungal triprenyl phenol metabolite

The aim of the present study was to establish a novel embolic model of cerebral infarction and to evaluate the effect of Stachybotrys microspora triprenyl phenol-7 (SMTP-7), a novel fungal triprenyl phenol metabolite. Thrombotic occlusion was induced by transfer of acetic acid-induced embolus into the brain. The regional cerebral blood flow was measured by a laser Doppler flowmeter to check the ischemic condition. Infarction area was assessed by 2% 2,3,5-triphenyltetrazolium chloride (TTC) staining. Neurological scores were determined by a modified version of the method described by Longa et al. Emboli were accumulated at the temporal or parietal region of the middle cerebral artery. Additionally, we found that this model showed decreased cerebral blood flow and increased infarction area and neurological scores. Treatment with tissue plasminogen activator (t-PA) reduced infarction area and the neurological scores in a dose-dependent manner; moreover, the decreased cerebral blood flow recovered. SMTP-7 also reduced these values. The therapeutic time window of SMTP-7 was longer than that of t-PA. These results indicate that this model may be useful for understanding the pathophysiological mechanisms of cerebral infarction and evaluating the effects of therapeutic agents. Additionally, SMTP-7 is a promising approach to extend the therapeutic time window. Therefore, this novel compound may represent a novel approach for the treatment of cerebral infarction.

A novel finding of a low-molecular-weight compound, SMTP-7, having thrombolytic and anti-inflammatory effects in cerebral infarction of mice

Tissue plasminogen activator (t-PA) has a short therapeutic time window for administration (3 h) and carries a risk of promoting intracerebral hemorrhage. The aim of the present study was to investigate a therapeutic time window and frequency of hemorrhagic region by treatment with Stachybotrys microspora triprenyl phenol-7 (SMTP-7). Thrombotic occlusion was induced by transfer of acetic acid-induced thrombus at the right common carotid artery into the brain of mice. Infarction area, neurological score, edema percentage, and regional cerebral blood flow (CBF) were determined as the index of the efficacy of SMTP-7. In order to evaluate the mechanism of SMTP-7, plasmin activities and the expressions of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-6 mRNA were examined. SMTP-7 (0.1, 1, 10 mg/kg) dose dependently reduced infarction area, neurological score, and edema percentage. Additionally, its therapeutic time window was longer than that of t-PA, a high-molecular-weight compound. In addition, little hemorrhagic region was induced by treatment with SMTP-7. SMTP-7 showed plasmin activity in vivo and caused a decreased CBF to recover. Furthermore, the expressions of inflammatory cytokine mRNA (IL-1β, TNF-α, IL-6) were increased by t-PA treatment 3 h after ischemia but were not induced by SMTP-7 treatment. These results indicate that SMTP-7 shows potential thrombolytic and anti-inflammatory effects as well as a wide therapeutic time window and little hemorrhagic region compared with that of t-PA. Therefore, this novel low-molecular-weight compound may represent a novel approach for the treatment of cerebral infarction.

Mechanistic insight into neurotoxicity of tissue plasminogen activator-induced thrombolysis products in a rat intraluminal middle cerebral artery occlusion model

Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) after ischemic stroke is effective. However, rtPA potentiates neuronal damage, and interactions between rtPA and thrombolysis products (TLP) have been reported to play a role in this. In the present study we investigated the mechanisms underlying rtPA- and TLP-induced neurotoxicity. Adult male Sprague-Dawley rats were subjected to 60-min intraluminal middle cerebral artery (MCA) occlusion, and then treated with rtPA (10 mg/kg), TLP, or saline. To evaluate the effects of a free radical scavenger, treatment with edaravone and TLP was evaluated. To investigate the role of red blood cells (RBCs), RBC-depleted TLP was used. Neurological deficit scores, infarct volume, and immuno-histochemical localization of oxidative end products for lipid and DNA (4-hydroxy-2-nonenal [4-HNE] and 8-hydroxy-deoxyguanosine [8-OHdG]) were evaluated. TLP increased the infarct volume, worsened the neurological deficits, and increased accumulations of 4-HNE and 8-OHdG. Edaravone treatment significantly reduced the lesion volume and improved the neurological score. Both infarct volume and accumulation of oxidative products were significantly suppressed when RBC-depleted TLP was used. In this mechanical model of MCA occlusion, rtPA-induced TLP, especially in the presence of RBCs, contributed to neuronal damage by accelerating free radical injury.