Neuronal Death In Stroke Research Articles

Melatonin exhibits antioxidant properties in a mouse brain slice model of excitotoxicity.

Stroke is a major cause of brain injury in Alaska. Since antioxidant levels are decreased in aged brain, the greater predisposition to neuronal death in stroke leading to subsequent neurodegeneration in aged individuals may be related to changes in oxidant balance. We studied the effect of the endogenous antioxidant melatonin on excitotoxic injury resulting from N-methyl-D-aspartate (NMDA)-induced damage by developing an organotypic mouse brain slice model. Our objective was to inhibit the effects of oxidative stress induced by NMDA in mouse brain slices, using melatonin. An organotypic mouse brain slice culture was established at PO2 levels maintained between 80 - 100 mm Hg. NMDA, melatonin or both were added to the slices and antioxidant function was determined using the redox active iron assay as well as 8-OHG and HO-1 immunoassays. This slice system allows for better regulation of both NMDA and melatonin concentrations than can be achieved by in vivo studies. Supporting an antioxidant function, melatonin (100 microM) significantly decreased redox active iron, heme-oxygenase (HO-1) induction and 8-hydroxyguanosine (8-OHG) following NMDA (50-100 microM) insult. However, somewhat surprisingly, high concentrations of melatonin alone (1 mM), increased redox active iron levels and HO-1 induction. These results support the hypothesis that melatonin is a neuroprotective antioxidant. Our data also suggest that 1 mM melatonin may have detrimental effects.

Melatonin exhibits antioxidant properties in a mouse brain slice model of excitotoxicity

Objectives. Stroke is a major cause of brain injury in Alaska. Since antioxidant levels are decreased in aged brain, the greater predisposition to neuronal death in stroke leading to subsequent neurodegeneration in aged individuals may be related to changes in oxidant balance. We studied the effect of the endogenous antioxidant melatonin on excitotoxic injury resulting from N-methyl-D-aspartate (NMDA)-induced damage by developing an organotypic mouse brain slice model. Our objective was to inhibit the effects of oxidative stress induced by NMDA in mouse brain slices, using melatonin. Methods. An organotypic mouse brain slice culture was established at PO2 levels maintained between 80 — 100 mm Hg. NMDA, melatonin or both were added to the slices and antioxidant function was determined using the redox active iron assay as well as 8-OHG and HO-1 immunoassays. Results. This slice system allows for better regulation of both NMDA and melatonin concentrations than can be achieved by in vivo studies. Supporting an antioxidant function, melatonin (100 µM) significantly decreased redox active iron, hemexygenase (HO-1) induction and 8-hydroxyguanosine (8-OHG) following NMDA (50–100 µM) insult. However, somewhat surprisingly, high concentrations of melatonin alone (1mM), increased redox active iron levels and HO-1 induction. Conclusions. These results support the hypothesis that melatonin is a neuroprotective antioxidant. Our data also suggest that 1mM melatonin may have detrimental effects.

The role of excitotoxicity in ALS--what is the evidence?

It is well accepted that excitotoxic mechanisms contribute to the pathogenesis of acute neuronal death in stroke, epilepsy, or brain trauma. It is less widely acknowledged that excitotoxic mechanisms play a role in the pathogenesis of chronic neurological disorders, in particular neurodegenerative diseases. However, evidence is accumulating that this mechanism is indeed part of the pathogenesis of late-onset neurodegenerative diseases. One of the clinical examples may be amyotrophic lateral sclerosis, a disease in which antiexcitotoxic strategies have neuroprotective effects in both, an established animal model and in man. In addition, there is accumulating neuropathological, pathobiochemical and pathophysiological evidence which indicates that excitotoxic mechanisms are part of the pathogenesis of the human disease and consequently part of the mechanisms explaining selective vulnerability ("pathoclisis") in the human motor system.

Apoptotic DNA fragmentation in the rat cerebral cortex induced by permanent middle cerebral artery occlusion.

Recent investigations have demonstrated internucleosomal DNA fragmentation in ischemic neuronal tissue. This type of fragmentation is characteristic of programmed cell death or apoptosis and suggests that neuronal death in stroke may be more complex than simple necrotic death. The present experiments provide a detailed examination of the regional localization and time course for apoptotic DNA fragmentation in the cerebral cortex following focal cerebral ischemia. Spontaneously hypertensive rats were subjected to permanent right middle cerebral artery occlusion and the cerebral cortices were examined for evidence of DNA fragmentation using electrophoretic, flow cytometric, and histological approaches. An electrophoretic examination of cortical DNA at 24 h after the occlusion indicated that the majority of nucleosomal ladders were in the transition zone or penumbra and the core of the infarction, with no fragmentation apparent in the contralateral normal cortex. A flow cytometric analysis of DNA fragmentation in intact cells revealed a similar pattern, with increased fragmentation observed in ischemic cortex vs. the contralateral cortex. Saggital sections taken 1.5 mm lateral to midline were collected from animals at 1, 4, and 24 h after the infarction and DNA fragmentation was examined histologically by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) staining. Quantitative analysis of these sections indicated that DNA fragmentation can be observed in the anterior and central area of the infarctions as soon as 1 h after the occlusion and that the extent and magnitude of the fragmentation increases at 4 and 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)