title: Caspases mediate 6-hydroxydopamine-induced apoptosis but not necrosis in PC12 cells.
abstract: The neurotoxin 6-hydroxydopamine (6-OHDA) induces apoptosis in the rat phaeochromocytoma cell line PC12. 6-OHDA-induced apoptosis is morphologically indistinguishable from serum deprivation-induced apoptosis. Exposure of PC12 cells to a low concentration of 6-OHDA (25 microM) results in apoptosis, whereas an increased concentration (50 microM) results in a mixture of apoptosis and necrosis. We investigated the involvement of caspases in the apoptotic death of PC12 cells induced by 6-OHDA, using a general caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk), and compared this with serum deprivation-induced apoptosis, which is known to involve caspases. We show that zVAD-fmk (100 microM) completely prevented the apoptotic morphology of chromatin condensation induced by exposure to either 6-OHDA (25 and 50 microM) or serum deprivation. Furthermore, cell lysates from 6-OHDA-treated cultures showed cleavage of a fluorogenic substrate for caspase-3-like proteases (caspase-2, 3, and 7), acetyl-Asp-Glu-Val-Asp-aminomethylcoumarin, and this was inhibited by zVAD-fmk. However, although zVAD-fmk restored total cell viability to serum-deprived cells or cells exposed to 25 microM 6-OHDA, the inhibitor did not restore viability to cells exposed to 50 microM 6-OHDA. These data show the involvement of a caspase-3-like protease in 6-OHDA-induced apoptosis and that caspase inhibition is sufficient to rescue PC12 cells from the apoptotic but not the necrotic component of 6-OHDA neurotoxicity.
authors.affiliation: School of Biological Sciences, University of Manchester, England, UK.
authors.forename: E E
authors.initials: EE
authors.lastname: Ochu
authors.forename: N J
authors.initials: NJ
authors.lastname: Rothwell
authors.forename: C M
authors.initials: CM
authors.lastname: Waters
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D003374:Coumarins / Q000494:pharmacology; D016895:Culture Media, Serum-Free; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009336:Necrosis; D009842:Oligopeptides / Q000494:pharmacology; D016627:Oxidopamine / Q000633:toxicity*; D016716:PC12 Cells; D051381:Rats
chemical_list: C112287:Ac-aspartyl-glutamyl-valyl-aspartyl-aminomethylcoumarin; D003374:Coumarins; D016895:Culture Media, Serum-Free; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; C103712:benzyloxycarbonyl-valyl-alanyl-aspartyl-fluoromethane; D016627:Oxidopamine; D003546:Cysteine Endopeptidases