Apoptosis and necrosis: two distinct events induced, respectively, by mild and intense insults with N-methyl-D-aspartate or nitric oxide/superoxide in cortical cell cultures.

Abstract

N-Methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity may depend, in part, on the generation of nitric oxide (NO.) and superoxide anion (O2.-), which react to form peroxynitrite (OONO-). This form of neurotoxicity is thought to contribute to a final common pathway of injury in a wide variety of acute and chronic neurologic disorders, including focal ischemia, trauma, epilepsy, Huntington disease, Alzheimer disease, amyotrophic lateral scelerosis, AIDS dementia, and other neurodegenerative diseases. Here, we report that exposure of cortical neurons to relatively short durations or low concentrations of NMDA, S-nitrosocysteine, or 3-morpholinosydnonimine, which generate low levels of peroxynitrite, induces a delayed form of neurotoxicity predominated by apoptotic features. Pretreatment with superoxide dismutase and catalase to scavenge O2.- partially prevents the apoptotic process triggered by S-nitrosocysteine or 3-morpholinosydnonimine. In contrast, intense exposure to high concentrations of NMDA or peroxynitrite induces necrotic cell damage characterized by acute swelling and lysis, which cannot be ameliorated by superoxide dismutase and catalase. Thus, depending on the intensity of the initial insult, NMDA or nitric oxide/superoxide can result in either apoptotic or necrotic neuronal cell damage.

Improved functional outcome after spinal cord injury in iNOS-deficient mice

“…NO derived from iNOS catalytic activity may react with the superoxide anion to form peroxynitrite, 9 a molecule that is associated with oxidative tissue damage 13 and apoptotic neuronal death. 14 In contrast to this, other investigators have shown that functional end points after controlled cortical impact brain trauma were significantly worsened if iNOS was pharmacologically inhibited or genetically deficient in experimental rats and mice, respectively. 6 Based upon this finding, it was hypothesised that iNOS is a postinjury endogenous neuroprotectant.…”

Elevated glutamate and lactate predict brain death after severe head trauma

“…Glutamate, the predominant excitatory neurotransmitter in the mammalian brain, may become excitotoxic at high extracellular concentrations through overstimulation of glutamate receptors 5, 10. Remarkably, high concentrations of extracellular glutamate are commonly observed after severe TBI, the magnitude of which correlates with increased intracranial pressure (ICP) and poor clinical outcomes 11, 12, 13, 14.…”

“…Immediately after TBI, there is an exacerbated glutamate‐induced neuronal calcium influx and ionic imbalance, which evokes membrane depolarization and further glutamate release. As consequence, the membrane pumps work to rapidly restore the membrane gradients thereby increasing the glucose flux through glycolytic pathway and lactate production 8, 10. However, extracellular lactate may arise not only from neuronal glycolysis.…”

Staged anticonvulsant screening for chronic epilepsy

“…2A). This may be due to different modes of cell death 27. We therefore adopted the following criteria for establishing toxicity of a given drug‐concentration pair: (1) morphology score >0, or (2) LDH on DIV 6/7 that was significantly higher than control.…”

“…Increases in extracellular lactate accompanied seizures in human hippocampus,25, 26 and we found that lactate production was correlated with seizure‐like activity in organotypic cultures. Lactate dehydrogenase (LDH) is released into culture medium after plasma membrane loses its integrity,27, 28, 29 and its concentration is correlated with cell death in cultures. We then demonstrated that this preparation and lactate and LDH assays can be used to evaluate anticonvulsant efficacy, using phenytoin and manipulation of mTOR pathway as examples 30, 31.…”