Imaging of reactive oxygen species in focal ischemic mouse brain using a radical trapping tracer [3H]hydromethidine

Kohji Abe,Miwa Ito,Kenji Morimoto,Misato Tonomura,Osamu Inoue,Kazumi Fukumoto,Natsumi Imamoto,Nozomi Takai,Sotaro Momosaki,Takemi Rokugawa

doi:10.1186/s13550-015-0115-1

Kohji Abe, Miwa Ito + Show 8 more

Open Access

https://doi.org/10.1186/s13550-015-0115-1

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Journal: EJNMMI Research	Publication Date: Jun 26, 2015
Citations: 41	License type: CC BY 4.0

Affiliation: Futaba (Japan), Shionogi (Japan)

Abstract

BackgroundReactive oxygen species (ROS) have been implicated in the pathophysiology of the brain after ischemic stroke. In this study, we investigate the generation of brain ROS after transient focal ischemia in mice using a radical trapping radiotracer, [3H]-labeled N-methyl-2,3-diamino-6-phenyl-dihydrophenanthridine ([3H]hydromethidine), which we recently reported as a ROS imaging probe. We also examined the effect of dimethylthiourea (DMTU), a hydroxyl radical scavenger, on brain ROS generation and infarct volume after transient focal ischemia in mice.Methods[3H]Hydromethidine was intravenously injected into mice at 1, 2, 5, and 7 h after transient middle cerebral artery occlusion (tMCAO), and then, the brain autoradiogram was acquired at 60 min after tracer injection. Brain infarct volumes at 24 h after tMCAO were assessed by 2,3,5-triphenyltetrazolium chloride staining.ResultsAccumulation of radioactivity was observed in the ipsilateral striatum and cortex at 1 h after tMCAO. The increase of radioactivity was attenuated at 2 h after tMCAO and then became maximized at 5 h. The high accumulation of radioactivity remained until 7 h after tMCAO. DMTU treatment significantly attenuated the accumulation of radioactivity in the ipsilateral hemisphere at 1, 5, and 7 h after tMCAO. Brain infarct volumes were also significantly reduced in DMTU-treated mice at 24 h after tMCAO.ConclusionsThese results indicated that [3H]hydromethidine is a useful radiotracer for detecting in vivo brain ROS generation such as hydroxyl radical after ischemic injury.

Highlights

Reactive oxygen species (ROS) have been implicated in the pathophysiology of the brain after ischemic stroke
We investigated the spatiotemporal changes of ROS generation after ischemia/reperfusion in the transient middle cerebral artery occlusion (tMCAO) model mouse using the radical trapping radiotracer [3H]hydromethidine
Brain ROS following tMCAO in mice pretreated with saline or DMTU Figure 2 shows typical autoradiograms of the brain obtained at 60 min after [3H]hydromethidine injection to mice treated with saline or DMTU (200 mg/kg, intraperitoneally (i.p.)) 30 min before tMCAO

Summary

Introduction

Reactive oxygen species (ROS) have been implicated in the pathophysiology of the brain after ischemic stroke. We investigate the generation of brain ROS after transient focal ischemia in mice using a radical trapping radiotracer, [3H]-labeled N-methyl-2,3-diamino-6-phenyl-dihydrophenanthridine ([3H]hydromethidine), which we recently reported as a ROS imaging probe. We examined the effect of dimethylthiourea (DMTU), a hydroxyl radical scavenger, on brain ROS generation and infarct volume after transient focal ischemia in mice. Reactive oxygen species (ROS) have been implicated in the pathogenesis of various neurological disorders, such as ischemia, trauma, and degenerative disease [1,2,3]. Oxidative stress can primarily lead to the formation of superoxide radical (O2 · −) and nitric oxide (·NO), and highly reactive ROS including hydroxyl.

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