Elsevier

Experimental Neurology

Volume 215, Issue 1, January 2009, Pages 95-100
Experimental Neurology

The lipophilic multifunctional antioxidant edaravone (radicut) improves behavior following embolic strokes in rabbits: A combination therapy study with tissue plasminogen activator

https://doi.org/10.1016/j.expneurol.2008.09.004Get rights and content

Abstract

Edaravone is a lipophilic drug with multiple mechanisms of action. Because edaravone is a promising drug candidate for the treatment of stroke, we tested the hypothesis that edaravone would be neuroprotective following cerebral ischemia using a rabbit embolic stroke model with a well-defined behavioral endpoint. Using the rabbit small clot embolic stroke model (RSCEM), a drug or drug combination is considered beneficial if it significantly increases the amount of microclots (mg) measured in brain that produce neurologic dysfunction in 50% of a group of animals (P50) compared to the control group. Edaravone (100 mg/kg, SC), increased the P50 value to 1.80 ± 0.24 mg (p < 0.05) when administered 5 min following embolization and increased P50 values by 195% and 161% (compared to control) when administered 1 and 3 h following embolization, respectively, but was inactive when applied 6 h following embolization, compared to the cumulative control group (P50 = 0.93 ± 0.16 mg). To simulate the design of current clinical trials, edaravone was also given following a standard tPA regimen, which by itself increased the P50 value to 2.72 ± 0.28 mg. When tPA was infused 1 h following embolization and edaravone was given 3 h following embolization, the P50 was 2.68 ± 0.56 mg. This study indicates that edaravone may have substantial therapeutic benefit for the treatment of AIS since it had a therapeutic widow of at least 3 h in rabbits. Edaravone can also be administered with a thrombolytic to improve behavior.

Introduction

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one, Radicut, MCI-186) is a low molecular weight free radical scavenger that readily crosses the blood brain barrier (BBB) (Watanabe et al., 2008, Yoshida et al., 2006). Based upon Japanese clinical trials in stroke patients Mitsubishi-Tokyo Pharmaceutical Inc (Tokyo, Japan) has obtained approval from the regulatory agency in Japan for the treatment of acute ischemic stroke (AIS) patients with edaravone if the drug was administered within 72 h of the ischemic event (Edaravone Study Group, 2003, Inatomi et al., 2006, Mishina et al., 2005, Toyoda et al., 2004, Watanabe et al., 2008, Yoshida et al., 2006). Suda et al. (2007) have recently claimed that edaravone can salvage the boundary zone of the infarct in patients (i.e. ischemic penumbra) and reduce the extent of edema, presumably resulting in clinical improvement. Recently, Yoshifumi (2007) reported preliminary findings of a clinical trial showing that patients treated with edaravone prior to administration of intravenous tPA had a reduced incidence of hemorrhage compared to tPA-treated patients. Thus, the Japanese experience with edaravone suggests that edaravone is superior, in many ways, to the failed Astra-Zeneca spin trap agent NXY-059 (Diener et al., 2008, Shuaib et al., 2007), but outside of Japan there has been little to no clinical development for the treatment of AIS. Although edaravone is purported to have significant benefit in stroke patients, there is an increased risk of renal toxicity associated with its administration (Hishida, 2007). It has been reported that approximately 45% of patients with edaravone-induced renal toxicity recover renal function after edaravone treatment is stopped (Hishida, 2007).

The preclinical experience with edaravone is quite extensive since it has been under development by Mitsubishi-Tokyo Pharmaceutical Inc. of Tokyo, Japan for over a decade (Watanabe et al., 2008, Yoshida et al., 2006). The main focus of edaravone has been its potential to scavenge free radicals. Edaravone is a potent lipid-soluble hyrdoxyl and peroxyl radical scavenger that can inhibit lipid peroxidation and prevent vascular endothelial cell injury (Watanabe et al., 2008, Yoshida et al., 2006). In rat ischemia models, edaravone lowered hydroxyl radical production, ischemic infarction and suppressed delayed neuronal death (Araki et al., 2003, Nakashima et al., 1999, Nito et al., 2003, Wu et al., 2000, Yoshida et al., 2005). Free radicals have been proposed to cause a vast array of injuries mediated by many different pathways following a stroke (Cherubini et al., 2005, Facchinetti et al., 1998, Floyd, 1999, Lapchak and Araujo, 2003, Nakashima et al., 1999, Siesjo et al., 1995, Siesjo and Siesjo, 1996). The oxidative stress that occurs after an ischemic stroke produces reactive oxygen species (ROS) like hydrogen peroxide (H2O2), hydroxyl radical (HOradical dot) and superoxide anion radical (O2radical dot−) that bring about membrane lipid peroxidation. Damage to membranes then disrupts tissue integrity leading to neuronal damage and consequent behavioral deficits (Siesjo et al., 1995, Siesjo and Siesjo, 1996). It is also possible that the free radical scavenging activities of edaravone are its ability to inhibit lipoxygenase (LOX), reduce apoptosis and prevent vascular damage (Higashi et al., 2006).

Thus, in the present study we evaluated the pharmacological effects of edaravone in a rabbit small clot embolic stroke model (RSCEM) as a basis for the further development of this type of multifunctional compound. The RSCEM (Lapchak et al., 2002, Lapchak et al., 2004a, Lapchak et al., 2007, Lapchak et al., 2004c) is produced by the injection of blood clots into the cerebral vasculature. A wide range of clots doses are injected in order to generate both normal and abnormal animals with various behavioral deficits, which can be measured quantitatively using a simple dichotomous rating scale (Lapchak et al., 2002, Lapchak et al., 2004a, Lapchak et al., 2007, Lapchak et al., 2004c). Using the RSCEM, the present study tested the hypothesis that edaravone would be useful to attenuate embolism-induced behavioral deficits. Moreover, since optimal doses of tPA do not eliminate all brain damage, even though tPA does increase cerebral reperfusion (reviewed in Lapchak, 2002a), we investigated the interaction between tPA and edaravone to determine whether there are any positive or negative interactions when the drugs are combined. To simulate the design of recent clinical trials with neuroprotective agents and thrombolytics, edaravone was administered following tPA when thrombolysis is complete.

Section snippets

Materials and methods

Male New Zealand white rabbits weighing 2 to 2.5 kg were purchased from Rabbit Source Farms, Ramona, CA. Rabbits were supplied food (alfalfa cubes) and water ad libitum while under quarantine in an enriched environment for at least 5 days prior to experimental use. Surgery was done in a sterile controlled environment with a room temperature between 22.8 and 23.2 °C. The Department of Veterans Affairs and Institutional Animal Care and Use Committee (IACUC) approved the surgical and treatment

Effect of bolus injections of edaravone on behavior following embolic strokes: defining the therapeutic window

In the first series of experiments, we administered either vehicle (DMSO) or bolus injections of edaravone SC starting 5 min following small clot embolization. Subsequently, behavioral analysis was conducted. As shown in Table 1, edaravone at 100 mg/kg significantly improved stroke-induced behavioral deficits. The P50 value measured for the edaravone-treated group was 1.80 ± 0.24 mg, compared to a P50 of 0.93 ± 0.16 mg for the control group. For this series of experiments, we used the cumulative

Discussion

Recent efforts in developing new therapeutic molecules that could be used to treat acute ischemic stroke have been extremely disappointing (O'Collins et al., 2006). Despite the failure of so many drugs in western countries, the Japanese have had what they consider to be a success, so we have decided to evaluate their claims independently. We established that edaravone has a therapeutic window of at least 3 h in the rabbit embolic stroke model. Because the primary component of the clinical score

Acknowledgment

This study was supported by a Merit Review grant from the Veterans Administration.

References (51)

  • Effect of a novel free radical scavenger, edaravone (MCI-186), on acute brain infarction. Randomized, placebo-controlled, double-blind study at multicenters

    Cerebrovasc. Dis.

    (2003)
  • AlbertsM.J.

    Hyperacute stroke therapy with tissue plasminogen activator

    Am. J. Cardiol.

    (1997)
  • ArakiY. et al.

    The free radical scavenger edaravone suppresses experimental closed duodenal loop-induced acute pancreatitis in rats

    Int. J. Mol. Med.

    (2003)
  • ClarkW.M. et al.

    The rtPA (alteplase) 0- to 6-hour acute stroke trial, part A (A0276g): results of a double-blind, placebo-controlled, multicenter study. Thrombolytic therapy in acute ischemic stroke study investigators

    Stroke

    (2000)
  • DienerH.C. et al.

    NXY-059 for the treatment of acute stroke: pooled analysis of the SAINT I and II Trials

    Stroke

    (2008)
  • FacchinettiF. et al.

    Free radicals as mediators of neuronal injury

    Cell. Mol. Neurobiol.

    (1998)
  • FloydR.A.

    Antioxidants, oxidative stress, and degenerative neurological disorders

    Proc. Soc. Exp. Biol. Med.

    (1999)
  • HaleyE.C. et al.

    A pilot dose-escalation safety study of tenecteplase in acute ischemic stroke

    Stroke

    (2005)
  • HigashiY. et al.

    Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a novel free radical scavenger, for treatment of cardiovascular diseases

    Recent Patents Cardiovasc. Drug Discov.

    (2006)
  • HishidaA.

    Clinical analysis of 207 patients who developed renal disorders during or after treatment with edaravone reported during post-marketing surveillance

    Clin. Exp. Nephrol.

    (2007)
  • InatomiY. et al.

    Efficacy of edaravone in cardioembolic stroke

    Intern. Med.

    (2006)
  • KurodaS. et al.

    Neuroprotective effects of a novel nitrone, NXY-059, after transient focal cerebral ischemia in the rat

    J. Cereb. Blood Flow Metab.

    (1999)
  • LapchakP.A.

    Development of thrombolytic therapy for stroke: a perspective

    Expert Opin. Investig. Drugs

    (2002)
  • LapchakP.A.

    NXY-059

    Centaur. Curr. Opin. Investig. Drugs

    (2002)
  • LapchakP.A.

    Carbamylated erythropoietin to treat neuronal injury: new development strategies

    Expert Opin. Investig. Drugs

    (2008)
  • Cited by (0)

    View full text