The Role of Oxidative Stress in Acute Ischemic Stroke-Related Thrombosis

Acute ischemic stroke is a serious life-threatening disease that affects almost 600 million people each year throughout the world with a mortality of more than 10%, while two-thirds of survivors remain disabled. However, the available treatments for ischemic stroke are still limited to thrombolysis and/or mechanical thrombectomy, and there is an urgent need for developing new therapeutic target. Recently, intravascular oxidative stress, derived from endothelial cells, platelets, and leukocytes, has been found to be tightly associated with stroke-related thrombosis. It not only promotes primary thrombus formation by damaging endothelial cells and platelets but also affects thrombus maturation and stability by modifying fibrin components. Thus, oxidative stress is expected to be a novel target for the prevention and treatment of ischemic stroke. In this review, we first discuss the mechanisms by which oxidative stress promotes stroke-related thrombosis, then summarize the oxidative stress biomarkers of stroke-related thrombosis, and finally put forward an antithrombotic therapy targeting oxidative stress in ischemic stroke.

Is edaravone harmful? (A placebo is not a control)

Edaravone is delivered by long-term daily intravenous infusions, yet the risk of infusion was not considered in the design or analysis of studies examining the efficacy of edaravone in ALS. A reappraisal of the pivotal edaravone study (Study 19) on which claims of efficacy are based suggests that this risk cannot be dismissed, that the efficacy of edaravone may be over-estimated, and that some differences between edaravone and placebo may not implicate the ALS disease process. When trial conditions may be harmful to both arms of a placebo-controlled trial, not only is it necessary that treatment prove superior to placebo, but also that treatment is better than no intervention. In Study 19, edaravone performed better than placebo, but both placebo and edaravone likely did worse than no intervention, an interpretation more in keeping with previous trial experience of drugs with similar mechanisms of action, and with previous trial experience with edaravone. Edaravone, as presently delivered, may be both ineffective and harmful.

Edaravone, a Synthetic Free Radical Scavenger, Enhances Alteplase-Mediated Thrombolysis

The combination of alteplase, a recombinant tissue plasminogen activator, and edaravone, an antioxidant, reportedly enhances recanalization after acute ischemic stroke. We examined the influence of edaravone on the thrombolytic efficacy of alteplase by measuring thrombolysis using a newly developed microchip-based flow-chamber assay. Rat models of embolic cerebral ischemia were treated with either alteplase or alteplase-edaravone combination therapy. The combination therapy significantly reduced the infarct volume and improved neurological deficits. Human blood samples from healthy volunteers were exposed to edaravone, alteplase, or a combination of alteplase and edaravone or hydrogen peroxide. Whole blood was perfused over a collagen- and thromboplastin-coated microchip; capillary occlusion was monitored with a video microscope and flow-pressure sensor. The area under the curve (extent of thrombogenesis or thrombolysis) at 30 minutes was 69.9% lower in the edaravone-alteplase- than alteplase-treated group. The thrombolytic effect of alteplase was significantly attenuated in the presence of hydrogen peroxide, suggesting that oxidative stress might hinder thrombolysis. D-dimers were measured to evaluate these effects in human platelet-poor plasma samples. Although hydrogen peroxide significantly decreased the elevation of D-dimers by alteplase, edaravone significantly inhibited the decrease. Edaravone enhances alteplase-mediated thrombolysis, likely by preventing oxidative stress, which inhibits fibrinolysis by alteplase in thrombi.

YAMATO Study (Tissue-Type Plasminogen Activator and Edaravone Combination Therapy)

Background and Purpose—

We investigated whether administration of edaravone, a free radical scavenger, before or during tissue-type plasminogen activator (tPA) can enhance early recanalization in a major arterial occlusion.

Methods—

The YAMATO study (Tissue-Type Plasminogen Activator and Edaravone Combination Therapy) is an investigator-initiated, multicenter (17 hospitals in Japan), prospective, randomized, and open-label study. Patients with stroke secondary to occlusion of the M1 or M2 portion of the middle cerebral artery and within 4.5 hours of the onset were studied. The subjects were randomly allocated to the early group (intravenous edaravone [30 mg] was started before or during tPA) and the late group (edaravone was started after tPA and the assessment of early recanalization).

Results—

One-hundred sixty-five patients (96 men; median age [interquartile range], of 78 [69–85] years) were randomized 1:1 to either the early group (82 patients) or the late group (83 patients). Primary outcome, defined as an early recanalization 1.5 hour after tPA, was observed in 53% of the early group and in 53% of the late group ( P =1.000). About secondary outcomes, the rate of significant recanalization of ≥50% was not different between the 2 groups (28% versus 34%; P =0.393). The symptomatic intracerebral hemorrhage has occurred in 4 patients (5%) in the early group and in 2 patients (2%) in the late group ( P =0.443). The favorable outcome (modified Rankin Scale score of 0–2) at 3 months was also similar between the groups (53% versus 57%; P =0.738).

Conclusions—

The timing of edaravone infusion does not affect the rate of early recanalization, symptomatic intracerebral hemorrhage, or favorable outcome after tPA therapy.

Clinical Trial Registration—

URL: http://www.umin.ac.jp/ctr/index-j.htm . Unique identifier: UMIN000006330.

Edaravone is a free radical scavenger that protects against laser-induced choroidal neovascularization in mice and common marmosets

Choroidal neovascularization (CNV) is a main characteristic in exudative type of age-related macular degeneration (AMD). Our study aimed to evaluate the effects of edaravone, a free radical scavenger on laser-induced CNV. CNV was induced by laser photocoagulation to the subretinal choroidal area of mice and common marmosets. Edaravone was administered either intraperitoneally twice a day for 2 weeks or intravenously just once after laser photocoagulation. The effects of edaravone on laser-induced CNV were evaluated by fundus fluorescein angiography, CNV area measurements, and the expression of 4-hydroxy-2-nonenal (4-HNE) modified proteins, a marker of oxidative stress. Furthermore, the effects of edaravone on the production of H2O2-induced reactive oxygen species (ROS) and vascular endothelial growth factor (VEGF)-induced cell proliferation were evaluated using human retinal pigment epithelium cells (ARPE-19) and human retinal microvascular endothelial cells, respectively. CNV areas in the edaravone-treated group were significantly smaller in mice and common marmosets. The expression of 4-HNE modified proteins was upregulated 3 h after laser photocoagulation, and intravenously administered edaravone decreased it. In in vitro studies, edaravone inhibited H2O2-induced ROS production and VEGF-induced cell proliferation. These findings suggest that edaravone may protect against laser-induced CNV by inhibiting oxidative stress and endothelial cell proliferation.

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.