Release of taurine in apoptotic cerebellar granule neurons in culture.
Cell shrinkage is a distinctive feature of apoptotic death, but the mechanisms leading to cell volume loss are unclear at present. Activation of pathways extruding intracellular osmolytes such as K+, Cl- and organic molecules may be part of these mechanisms. This was examined in the present work measuring the release of taurine, gamma-amino-butyric acid (GABA) and glutamate in cerebellar granule neurons cultured in conditions resulting in apoptotic death after 4-7 days in vitro (DIV). The basal release of [3H]taurine from cells started to increase (38%) after 3 DIV and reached a maximal enhancement (250%) at 5 DIV. The increase in taurine efflux closely followed the occurrence of apoptotic death markers such as caspase induction and chromatin condensation. The efflux of glutamate (traced as D-aspartate) and [3H]GABA also increased but notably less than that of taurine (90% and 75%, respectively) at 5 DIV. Taurine release associated with apoptosis was unaffected by 4,4'-diisothiocyanatostilbene 2,2'-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), blockers of the diffusive pathway activated during cell volume regulation in hyposmotic conditions. Taurine efflux was increased in Cl(-)-free (replaced by gluconate) and decreased in Na+-free media. Blockers of the energy-dependent glutamate and taurine carriers, dihydrokainate and guanidinoethane sulfonate, respectively, did not affect the release associated with apoptosis. These results implicate taurine in the mechanism of cell shrinkage during apoptosis.
Morán
J
J
Department of Biophysics, Institute of Cell Physiology, National University of Mexico, Mexico City. jmoran@ifisiol.unam.mx
Hernández-Pech
X
X
Merchant-Larios
H
H
Pasantes-Morales
H
H
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D004396:Coloring Agents; D004058:Diffusion; D004792:Enzyme Precursors / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D013654:Taurine / Q000378:metabolism*; D013778:Tetrazolium Salts; D013844:Thiazoles; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018118:Chloride Channels; D004396:Coloring Agents; D004792:Enzyme Precursors; D013778:Tetrazolium Salts; D013844:Thiazoles; D013654:Taurine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D012964:Sodium; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue