https://www.sciencedirect.com/science/article/pii/S0891584917312790
Highlights
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- The nitrone 5 decomposes after reaction with ROS to the NOS inhibitor (6).
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- 5 showed neuroprotection through in vitro and in vivo models of ischemia.
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- 6 but not 5 exhibited a dose-dependent decrease in microglial NO production.
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- 6 is formed preferentially under oxidative stress conditions in vitro and in vivo.
Abstract
Ischemic
stroke is caused by a blockage of cerebral blood flow resulting in
neuronal and glial hypoxia leading to inflammatory and reactive oxygen
species (ROS)-mediated cell death. Nitric oxide (NO) formed by NO
synthase (NOS) is known to be protective in ischemic stroke, however NOS
has been shown to ‘uncouple’ under oxidative conditions to instead
produce ROS. Nitrones are antioxidant molecules that are shown to trap
ROS to then decompose and release NO. In this study, the nitrone 5was designed such that its decomposition product is a NOS inhibitor, 6, effectively leading to NOS inhibition specifically at the site of ROS production. The ability of 5to spin-trap radicals and decompose to 6 was observed using EPR and LC-MS/MS. The pro-drug concept was tested in vitro by measuring cell viability and 6 formation in SH-SY5Y cells subjected to oxygen glucose deprivation (OGD). 5
was found to be more efficacious and more potent than PBN, and was able
to increase phospho-Akt while reducing nitrotyrosine and cleaved
caspase-3 levels. 6 treatment, but not 5,
was found to decrease NO production in LPS-stimulated microglia.
Doppler flowmetry on anesthetized mice showed an increased cerebral
blood flow upon intravenous administration of 1 mg/kg 5,
but a return to baseline upon administration of 10 mg/kg, likely due to
its dual nature of antioxidant/NO-donor and NOS-inhibition. Mice
treated with 5 after permanent ischemia exhibited a >30% reduction in infarct volume, and higher formation 6 in ischemic tissue resulting in region specific effects limited to the infarct area.
Keywords
- Nitrone;
- Reactive Oxygen Species;
- Nitric Oxide;
- Nitric Oxide Synthase;
- Stroke;
- Ischemia
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