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DIFFERENTIAL SENSITIVITY OF ASTROCYTES TO FREE RADICALS: MYTOCHONDRIAL DYSFUNCTION AND TOXICITY C.J. Feeney,
A. Gyalkhandanyan, M.V. Frantseva, P.L. Carlen and P.S. Pennefather
Free radicals (FR) are highly reactive physiological metabolites, the production of which is greatly increased during pathological states. The CNS is considered to be particularly vulnerable to FR induced damage because of its high oxygen consumption and high levels of polyunsaturated lipids. There is increasing interest in the mechanisms by which glia modulate, and are targets of FR induced brain damage. Due to higher content of antioxidants, lower metabolic rates and lower concentrations of polyunsaturated lipids, astrocytes have been considered to be highly resistant to FR mediated damage. Our recent experiments however, suggest that astrocytes in cultured hippocampal slices are quite vulnerable to a FR-generating compounds (i.e. H2O2). To confirm and extend these findings, experiments were initiated on dissociated cultures of rat brain astrocytes. Cell death in cultures exposed to H2O2 was followed by fluorescent microscopy of propidium iodide (PI) labeling for up to 24 hours. H2O2 at concentrations as low as 50 ?M was found to cause massive cell death in hippocampal astrocyte cultures, whereas cortical astrocytes were found to be much more resistant. Utilizing the mitochondrial dye JC-1, we have shown that astrocytes from hippocampus, but not cortex, show a massive and rapid loss of mitochondrial membrane potential within 30-45 minutes H2O2 exposure, followed by rapid PI labeling. We have begun to determine the extent of metal ion involvement. Preliminary evidence suggests that transition metals (e.g. copper) are important contributors in astrocyte toxicity in response to FR-induced injury in vitro. Work continues to extend these findings, and to determine the nature and site of action of copper in the pathway of FR-induced cell damage in astrocytes.
For further information contact...Carmen Mannella: carmen@wadsworth.org |
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