Involvement of caspase-like proteinases in apoptosis of neuronal PC12 cells and primary cultured microglia induced by 6-hydroxydopamine.
Activation of proteolytic enzymes, including the caspase family of proteinases, is a feature characteristic of the apoptotic program. In the present study, we examined a potential role of intracellular proteinases in the death of neuronal PC12 and primary cultured rat microglial cells induced by 6-hydroxydopamine (6-OHDA). In both neuronal PC12 and microglial cells, 6-OHDA (10-200 microM) induced apoptosis in a dose-dependent manner as judged by the DNA break. The 6-OHDA was ineffective in Bcl-2-overexpressing neuronal PC12 cells. Pretreatment of these cells with two caspase inhibitors, acetyl-Try-Val-Ala-Asp-aldehyde and acetyl-Asp-Glu-Val-Asp-aldehyde, prevented the 6-OHDA-induced apoptosis. Pepstatin A and leupeptin, potent inhibitors of aspartic and cysteine proteinases, respectively, partly inhibited the apoptosis of microglia but not neuronal PC12 cells. In contrast, GBR12935, a dopamine uptake inhibitor, significantly inhibited the apoptotic death of neuronal PC12 cells but not microglia. These results suggest that mechanisms by which 6-OHDA induces apoptosis in these two cell types are distinct; 6-OHDA incorporated into neuronal PC12 cells and its metabolites may activate the caspase-like enzymes, whereas oxidative metabolites of the agent produced extracellularly may activate the caspase and the endosomal/lysosomal proteolytic systems in microglia.
Takai
N
N
Department of Pharmacology, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Nakanishi
H
H
Tanabe
K
K
Nishioku
T
T
Sugiyama
T
T
Fujiwara
M
M
Yamamoto
K
K
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004790:Enzyme Induction; D019254:Genes, bcl-2; D020287:In Situ Nick-End Labeling; D008024:Ligands; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016627:Oxidopamine / Q000494:pharmacology*; D016716:PC12 Cells; D010879:Piperazines / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats
D008024:Ligands; D010879:Piperazines; D011480:Protease Inhibitors; D016627:Oxidopamine; C044630:1-(2 (diphenylmethoxy)ethyl)-4-(3-phenylpropyl)piperazine; D020169:Caspases