thapsigargin and acetyl-aspartyl-glutamyl-valyl-aspartal

This study reports on the regulation of kainate neurotoxicity in cerebellar granule cells by calcium entry through voltage-gated calcium channels and by calcium release from internal cellular stores. Kainate neurotoxicity was prevented by the AMPA selective antagonist LY 303070 (10 microM). Kainate neurotoxicity was potentiated by cadmium, a general voltage-gated calcium channel blocker, and the L-type voltage-gated calcium channel blocker nifedipine. The antagonists of intracellular Ca2+ ([Ca2+]i) release, thapsigargin and ryanodine, were also able to potentiate kainate neurotoxicity. Kainate treatment elevated [Ca2+]i concentration with a rapid initial increase that peaked at 1543 nM and then declined to plateau at approximately 400 nM. Nifedipine lowered the peak response to 764 nM and the plateau response to approximately 90 nM. Thapsigargin also lowered the kainate-induced increase in [Ca2+]i (640 nM peak, 125 nM plateau). The ryanodine receptor agonist caffeine eliminated the kainate-induced increase in [Ca2+]i, and reduced kainate neurotoxicity. Kainate neurotoxicity potentiated by nifedipine was not prevented by RNA or protein synthesis inhibitors, nor by the caspase inhibitors YVAD-CHO and DEVD-CHO. Neither DNA laddering nor the number of apoptotic nuclei were increased following treatment with kainate and nifedipine. Increased nuclear staining with the membrane impermeable dye propidium iodide was observed immediately following kainate treatment, indicating a loss of plasma membrane integrity. Thus, kainate neurotoxicity is prevented by calcium entry through L-type calcium channels.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Apoptosis; Benzodiazepines; Calcium; Calcium Channel Blockers; Calcium Channels; Calcium Channels, L-Type; Cell Survival; Cells, Cultured; Cerebellum; Cysteine Proteinase Inhibitors; Dizocilpine Maleate; Electric Conductivity; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Ion Channel Gating; Kainic Acid; Necrosis; Neurons; Nifedipine; Oligopeptides; Phosphodiesterase Inhibitors; Rats; Ryanodine; Sodium; Sucrose; Thapsigargin

Thapsigargin, an endoplasmic reticular Ca2+-ATPase inhibitor, induced apoptotic cell death (chromatin condensation and DNA fragmentation) accompanied by the activation of CPP32-like protease, a member of the interleukin-1beta converting enzyme protease (ICE) family, but not the activation of ICE-like protease. Nerve growth factor (NGF) completely inhibited the cell death and CPP32-like activation induced by thapsigargin while Ac-Asp-Glu-Val-Asp-CHO, an inhibitor of CPP32-like protease, reduced the cell death. PD98059, a specific inhibitor of Map kinase kinase, did not reduce the protective effect of NGF on thapsigargin-induced cell death. These results suggest that calcium ion-induced apoptotic cell death was mediated by CPP32-like, but not ICE-like, protease and was regulated by a neurotrophic factor possibly, through the Map kinase cascade independent pathway.

Topics: Animals; Apoptosis; Calcium; Calcium-Transporting ATPases; Caspase 1; Caspase 3; Caspases; Cycloheximide; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Enzyme Activation; Enzyme Inhibitors; Flavonoids; L-Lactate Dehydrogenase; Mitogen-Activated Protein Kinase Kinases; Nerve Growth Factors; Neurons; Oligopeptides; PC12 Cells; Protein Kinase Inhibitors; Protein Synthesis Inhibitors; Rats; Thapsigargin