Abstract WMP119: Neurovascular Unit Protection Using Nitroxide Radicals-containing Nanoparticles (TEMPO-RNP) for Cerebral Ischemia-reperfusion Injury in Mice

Purpose: Reperfusion injury after thrombolytic therapy or mechanical thrombectomy would adverse neurological outcome. Generation of reactive oxygen species (ROS) due to reperfusion is relevant for aggravation. The development of drug therapy for scavenging free radical is expected to lead to better neurological prognosis. We developed a new core-shell type nanoparticle, RNP (radical containing nanoparticle), which consists of micelle containing 4-amino-TEMPO. The purpose of this study is to evaluate an efficacy of intra-arterial injection of RNP after reperfusion using tMCAO mice model.

Methods: C57BL/6J mice underwent tMCAO for 60 minutes and received RNP by intra-arterial injection from common carotid artery. We evaluated infarction size, neurological scale, and Evans blue extravasation at 24h after reperfusion. RNP distribution was detected by rhodamine labeling. We further examined immunofluorescense of CD31, Occludin, TUNEL, dihydroethydium, and 8-hydroxy-deoxyguanosine (8-OHdG). Multiple free radical scavenging capacity of ischemic hemisphere was analyzed by Electron Paramagnetic Resonance (EPR).

Results: RNPs were detected in endothelial cells and around neuronal cells in the ischemic lesion. The infarction size, neurological scale, Evans blue extravasation of the mice treated by RNP were significantly lower than the mice treated by PBS , control group. Intra-arterial RNP treatment preserved endothelium and expression of occludin in the ischemic brain. Further, apoptosis of neuronal cells and production of superoxide anions and 8OHdG were suppressed. By using EPR, multiple ROS scavenging capacity (•OH, •ROO, •O 2 - ) of the ischemic brain treated by RNP were higher.

Conclusions: These results suggest that intra-arterial injection of RNP have efficacy of neurovascular unit protection and reduce infarction volume by improving multiple ROS scavenging capacity.

Neurovascular Unit Protection From Cerebral Ischemia-Reperfusion Injury by Radical-Containing Nanoparticles in Mice

BACKGROUND AND PURPOSE

Reperfusion therapy by mechanical thrombectomy is used to treat acute ischemic stroke. However, reactive oxygen species generation after reperfusion therapy causes cerebral ischemia-reperfusion injury, which aggravates cerebral infarction. There is limited evidence for clinical efficacy in stroke for antioxidants. Here, we developed a novel core-shell type nanoparticle containing 4-amino-4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (nitroxide radical-containing nanoparticles [RNPs]) and investigated its ability to scavenge reactive oxygen species and confer neuroprotection.

METHODS

C57BL/6J mice underwent transient middle cerebral artery occlusion and then received RNPs (9 mg/kg) through the common carotid artery. Infarction size, neurological scale, and blood-brain barrier damage were visualized by Evans blue extravasation 24 hours after reperfusion. RNP distribution was detected by rhodamine labeling. Blood-brain barrier damage, neuronal apoptosis, and oxidative neuronal cell damage were evaluated in ischemic brains. Multiple free radical-scavenging capacities were analyzed by an electron paramagnetic resonance-based method.

RESULTS

RNPs were detected in endothelial cells and around neuronal cells in the ischemic lesion. Infarction size, neurological scale, and Evans blue extravasation were significantly lower after RNP treatment. RNP treatment preserved the endothelium and endothelial tight junctions in the ischemic brain; neuronal apoptosis, O₂^- production, and gene oxidation were significantly suppressed. Reactive oxygen species scavenging capacities against OH, ROO, and O₂^- improved by RNP treatment.

CONCLUSIONS

An intra-arterial RNP injection after cerebral ischemia-reperfusion injury reduced blood-brain barrier damage and infarction volume by improving multiple reactive oxygen species scavenging capacities. Therefore, RNPs can provide neurovascular unit protection.