Introduction
Edaravone is a potent free radical scavenger, which is known to reduce the size of infarction in animal experiments and clinical applications. The aim of this study is to observe sequentially the effect of this unique antioxidant against the photochemically induced cerebral infarction in the non-invasive way using the higher magnetic field MRI device.
Methods
C57BL/6J mice (25–30 g) were anesthetized by the intraperitoneal injection of chloralose and urethane mixture, keeping the rectal temperature at 37.5 degrees on the thermo-regulated heating pad (Nihon Kohden, ATB-1100). Photothrombosis (PT) was created in the right parietal lobe by the stereotactic illumination of the laser-diode light (532 nm, 5 mW) for 30 minutes after the injection of rose-bengal solution via the tail vein. Cerebral blood flow was measured on the right parietal lobe using the laser-Doppler flow meter (Advance, ALF21), and the mean arterial pressure with heart rate was monitored throughout the experiment from the tail artery (Muromachi, MK-2000). Animals were divided into the ischemic control (C) group (N=6), and edaravone (E) group (N=6) treated twice (3 mg/kg iv, each time), immediately before and after PT. Cerebral images were taken by the 9.4 T MRI (Bruker, AVANCE400WB) at 1- and 3-hour, 1- and 3-day, and 1-week after PT in individual mice. Ischemic changes were measured sequentially in T1+Gd-DTPA (PWI), Diffusion (DWI), and T2 weighted images (20 mm FOV, 256×128 matrix, coronal slice) by the ROI analysis program. Small numbers of mice were used for the videomicroscopic observation through the cranial window and the morphological analysis.
Results
Microscopic observation through cranial windows showed diffuse cortical vessel occlusions by homogenous thrombi in the C group, indicating the enough ischemic insult by 30-minutes irradiation of green light laser. In the C group, MR images showed moderate ischemic changes in PWI and DWI at 1-hour. T2 changes appeared at 3-hour, further enlarging in size at 1- and 3-day, and then subsided at 1-week. These edematous changes apparently reduced in the E group. The cross-sectional size of ischemic T2 changes occupied 36.2±1.9% (M±SEM) of the ipsilateral hemisphere at 3-day in the C group, and it decreased to 9.6±2.6% (p<0.05) in the E group.
Conclusion
Free radical scavenger, edaravone, markedly decreased the size of ischemic changes induced by photothrombosis. One mechanism of protection may be due to the reduction of the post-ischemic inflammatory process through blocking the dissociation of NFkB and IkB by free radicals. Another mechanism might be the attenuation of blood brain barrier disruptions by interfering free radical reactions initiated by singlet oxygen molecules generated photochemically at endothelium 1 . Further analysis will be required.