anisomycin and Nerve-Degeneration

We examined the behavior of the transcription factor Max during retrograde neuronal degeneration of retinal ganglion cells. Using immunohistochemistry, we found a progressive redistribution of full-length Max from the nucleus to the cytoplasm and dendrites of the ganglion cells following axon damage. Then, the axotomized cells lose all their content of Max, while undergoing nuclear pyknosis and apoptotic cell death. After treatment of retinal explants with either anisomycin or thapsigargin, the rate of nuclear exclusion of Max accompanied the rate of cell death as modulated by either drug. Treatment with a pan-caspase inhibitor abolished both TUNEL staining and immunoreactivity for activated caspase-3, but did not affect the subcellular redistribution of Max immunoreactivity after axotomy. The data show that nuclear exclusion of the transcription factor Max is an early event, which precedes and is independent of the activation of caspases, during apoptotic cell death in the central nervous system.

Topics: Animals; Anisomycin; Apoptosis; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Basic-Leucine Zipper Transcription Factors; Blotting, Western; Caspases; Cells, Cultured; DNA-Binding Proteins; Enzyme Inhibitors; Immunohistochemistry; In Situ Nick-End Labeling; Nerve Degeneration; Protein Synthesis Inhibitors; Protein Transport; Rats; Retinal Ganglion Cells; Thapsigargin; Time Factors; Transcription Factors

Growing evidence suggests that non-N-methyl-D-aspartate receptor activation may contribute to neuronal death in both acute and chronic neurological diseases. The intracellular processes that mediate this form of neuronal death are poorly understood. We have previously characterized a model of kainate neurotoxicity using cerebellar granule cell neurons in vitro and we sought to determine the mechanism of kainate-induced neurons degeneration. We found DNA, and chromatin condensation using a fluorescent DNA intercalating dye, in cerebellar granule cells following exposure to kainate (100 microM). Aurintricarboxylic acid protected cerebellar granule cells from kainate-induced death. While the morphological and biochemical features of neuronal death induced by kainate resembled low-K(+)-induced apoptosis in cerebellar granule cells; the time interval from the institution of the death-promoting condition to neuronal death was briefer with kainate and did not require new protein or RNA synthesis. These results demonstrate that kainate receptor activation can induce transcription-independent apoptosis in neurons. This in vitro model should be useful in identifying the intracellular pathways that link kainate receptor activation with apoptosis.

Topics: Animals; Anisomycin; Apoptosis; Aurintricarboxylic Acid; Cell Nucleus; Cerebellum; Cycloheximide; Dactinomycin; DNA; Electrophoresis, Agar Gel; Kainic Acid; Kinetics; Nerve Degeneration; Neurons; Neurotoxins; Rats; Rats, Sprague-Dawley