Article
Neuroprotective effect of radical-containing nanoparticle (RNP) after cerebral ischemia-reperfusion injury
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Published: | June 4, 2012 |
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Objective: Neuroprotection is an essential treatment strategy for prevention of the ischemia-reperfusion injury, but a clinically available medicine is limited. Therefore, we developed a newly free radical sacavenger of core-shell-type nanoparticles (micelles) containing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), termed a radical-containing nanoparticle (RNP), which had a prolonged half-life of TEMPO radicals and pH-sensitivity to make them act in the low pH condition such as ischemic lesion. (Yoshitomi, et.al. Biomacromolecules 2009). This time, we evaluated that the abilities of RNP to deliver TEMPO radicals in the ischemic brain and scavenge free radicals after cerebral ischemia-reperfusion injury using a transient cerebral ischemia model in rats.
Methods: The delivery of TEMPO radicals in RNP was evaluated by electron paramagnetic resonance (EPR) and fluorescence analysis. The production of superoxide anion in neuronal cells was examined by dihydroethidium staining. The treatment effects were evaluated by measuring the cerebral infarction volumes, evans blue extravasation, neurological symptom, lipid peroxidation and protein oxidation. The adverse events were evaluated with physiological parameters.
Results: The TEMPO radicals in RNPs were detected for 6 h after intravenous administration as an EPR signal in the ischemic brain, and distributed on the endothelial cells of the cerebral infarct area. RNPs significantly reduced superoxide anion in neuronal cells as compared to saline and TEMPOL. The infarct volume and extravasation of evans blue treated by RNPs were significantly lower than those of rats treated by saline, micelles, and TEMPOL. In addition, RNP treatment suppressed lipid peroxidation and protein oxidation, and limited the adverse effects of TEMPO radicals, such as hypotension.
Conclusions: RNPs could be a promising neuroprotective agent with the enhanced ability of TEMPO radicals and the reduced toxicity. (Marushima, et.al, Neurosurgery 2011)