Comparative transcriptome of neurons after oxygen-glucose deprivation: Potential differences in neuroprotection versus reperfusion.

In the context of ischemic stroke, rescuing neurons can be theoretically achieved with either reperfusion or neuroprotection. Reperfusion works via the rapid restoration of oxygen and glucose delivery. Neuroprotection comprises molecular strategies that seek to block excitotoxicity, oxidative stress or various cell death pathways. Here, we propose the hypothesis that neurons rescued with reperfusion are different from neurons rescued with molecular neuroprotection. Neurons were subjected to oxygen-glucose deprivation (OGD) and then treated with "in vitro reperfusion" (i.e. energetic rescue via restoration of oxygen and glucose) or Z-VADfmk (to block apoptosis) or MK-801 (to block excitotoxicity). Levels of injury were titrated so that equivalent levels of neuronal salvage were achieved with reperfusion or neuroprotection. Gene arrays showed that OGD significantly altered the transcriptomic profiles of surviving neurons. Pathway analysis confirmed that a large spectrum of metabolic, inflammation, and signaling genes were perturbed. In spite of the fact that equal levels of neuronal salvage were achieved, energetic rescue renormalized the transcriptomic profiles in surviving neurons to a larger degree compared to neuroprotection with either Z-VADfmk or MK-801. These findings suggest that upstream reperfusion may bring salvaged neurons back "closer to normal" compared to downstream molecular neuroprotection.

Plasmalemma permeability and necrotic cell death phenotypes after intracerebral hemorrhage in mice.

BACKGROUND AND PURPOSE: Traumatic and ischemic brain injury induce plasmalemma permeability and necrosis; however, no studies have examined these aspects of cellular injury in intracerebral hemorrhage models. METHODS: In vivo propidium iodide (PI) and YOYO-1 were used to assess plasmalemma damage after collagenase-induced intracerebral hemorrhage in mice. Ex vivo aspartylglutamylvalylaspartic acid, terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, and electron microscopy were used to assess the relationship between plasmalemma permeability and mode of cell death. Cell types vulnerable to plasmalemma damage were determined by immunohistochemistry. RESULTS: Plasmalemma permeability was first detected in the lesion at 1 to 3 hours and peaked at 48 to 72 hours. Neurons and IBA-1-positive cells with morphological features of monocytes were sensitive, whereas resident microglia and astrocytes were resistant to plasmalemma permeability. PI+ cells colocalized with fluorescent-labeled caspase substrates and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling beginning at 3 to 6 hours. At 48 hours, greater than half of injured cells were PI+/aspartylglutamylvalylaspartic acid- or PI+/terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling- suggesting necrosis, and <5% were PI-/terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling+ or PI-/aspartylglutamylvalylaspartic acid+. Electron microscopy confirmed ultrastructural features of necrosis at 24 hours after intracerebral hemorrhage, high mobility group box protein-1 was released from permeable cells, and mice deficient in receptor interacting protein kinase (RIPK) 3, a known necrosis trigger, had 50% less PI+ cells at 24 hours. Permeable cells remained in the brain for at least 24 hours with <10% spontaneous resealing. CONCLUSIONS: Necrosis contributes to cell demise after intracerebral hemorrhage. Programmed necrosis and plasmalemma damage may represent novel therapeutic targets to prevent cell death or rescue injured cells after intracerebral hemorrhage.