Neuroprotection by the stable nitroxide Tempol during reperfusion in a rat model of transient focal ischemia.
OBJECTIVE
The use of thrombolytic agents in the treatment of stroke has yielded surprisingly modest success, possibly because of reperfusion injury mediated by reactive oxygen species (ROS). Therefore, scavenging ROS may be of therapeutic value in the treatment of stroke. Nitroxides are low-weight superoxide dismutase mimics, which allows them to act as cell-permeable antioxidants. In this study the nitroxide 4-hydroxy-2,2,6,6,-tetramethylpiperidine-1-oxyl (Tempol) is investigated to determine its ability to reduce reperfusion injury.


METHODS
Male Sprague-Dawley rats weighing between 280 g and 350 g underwent middle cerebral artery occlusion with an intraluminal suture for 60 minutes. Regional cerebral blood flow, blood pressure, cerebral temperature, and rectal temperature were monitored during the procedure. After reperfusion, the animals were randomized to groups receiving blinded intravenous administration of either Tempol (10 mg/kg; eight animals) or vehicle (eight animals) over the first 20 minutes of reperfusion (Study I). In a second study to determine dose dependency, animals were randomized to groups receiving Tempol (20 mg/kg; eight animals), low-dose Tempol (5 mg/kg; eight animals), or vehicle (eight animals; Study II). The rats were killed after 4 hours of reperfusion, and brain sections were stained with 2,3,5 triphenyltetrazolium chloride. Infarct volumes were measured using digital imaging. Animals receiving Tempol had significantly reduced infarct volumes at doses of 20 mg/kg and 10 mg/kg compared with controls (49.01+/-18.22% reduction [p = 0.003] and 47.47+/-34.57 [p = 0.02], respectively). No significant differences in the physiological variables measured were observed between groups.


CONCLUSIONS
Tempol provides significant neuroprotection after reperfusion in a rat model of transient focal ischemia. These results support the importance of ROS in reperfusion injury and encourage further study of this molecule as a therapeutic agent following thrombolysis.
Rak
R
R
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
Chao
D L
DL
Pluta
R M
RM
Mitchell
J B
JB
Oldfield
E H
EH
Watson
J C
JC
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D001921:Brain / Q000187:drug effects; D002544:Cerebral Infarction / Q000473:pathology / Q000517:prevention & control; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004396:Coloring Agents; D003497:Cyclic N-Oxides / Q000008:administration & dosage / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000008:administration & dosage / Q000627:therapeutic use; D007091:Image Processing, Computer-Assisted; D007275:Injections, Intravenous; D002546:Ischemic Attack, Transient / Q000150:complications* / Q000473:pathology; D008297:Male; D018696:Neuroprotective Agents / Q000627:therapeutic use*; D014677:Pharmaceutical Vehicles; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D016037:Single-Blind Method; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000627:therapeutic use; D013778:Tetrazolium Salts
D000975:Antioxidants; D004396:Coloring Agents; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D018696:Neuroprotective Agents; D014677:Pharmaceutical Vehicles; D017382:Reactive Oxygen Species; D013113:Spin Labels; D013778:Tetrazolium Salts; C009591:triphenyltetrazolium; D013482:Superoxide Dismutase; C001803:tempol