title: Mechanisms of antiapoptotic effects of estrogens in nigral dopaminergic neurons.
abstract: Parkinson's disease is characterized by the mesencephalic dopaminergic neuronal loss, possibly by apoptosis, and the prevalence is higher in males than in females. The estrogen receptor (ER) subtype in the mesencephalon is exclusively ER beta, a recently cloned novel subtype. Bound with estradiol, it enhances gene transcription through the estrogen response element (ERE) or inhibits it through the activator protein-1 (AP-1) site. We demonstrated that 17beta-estradiol provided protection against nigral neuronal apoptosis caused by exposure to either bleomycin sulfate (BLM) or buthionine sulfoximine (BSO). BLM and BSO-induced nigral apoptosis was blocked by inhibitors for caspase-3 or c-Jun/AP-1. The antiapoptotic effect by estradiol was blocked by ICI 182,780, an antagonist for ER, but not by a synthesized peptide that inhibits binding of the ER to the ERE. Estradiol had no effects on caspase-3 activation and c-Jun NH(2)-terminal kinase (JNK), which were activated by BLM. It also suppressed apoptosis by serum deprivation, which was independent of caspase-3 activation. Therefore, the antiapoptotic neuroprotection by estradiol is mediated by transcription through AP-1 site downstream from JNK and caspase-3 activation. Furthermore, 17alpha-estradiol, a stereoisomer without female hormone activity, also provided an antiapoptotic effect. Therefore, the antiapoptotic effect is independent of female hormone activity.
authors.affiliation: Department of Neurology, Graduate School of Medicine, Kyoto University, Sakyoku, Kyoto 606-8507, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sawada
authors.forename: M
authors.initials: M
authors.lastname: Ibi
authors.forename: T
authors.initials: T
authors.lastname: Kihara
authors.forename: M
authors.initials: M
authors.lastname: Urushitani
authors.forename: K
authors.initials: K
authors.lastname: Honda
authors.forename: M
authors.initials: M
authors.lastname: Nakanishi
authors.forename: A
authors.initials: A
authors.lastname: Akaike
authors.forename: S
authors.initials: S
authors.lastname: Shimohama
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001761:Bleomycin / Q000037:antagonists & inhibitors / Q000633:toxicity; D019328:Buthionine Sulfoximine / Q000037:antagonists & inhibitors / Q000633:toxicity; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004298:Dopamine / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D047629:Estrogen Receptor beta; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011960:Receptors, Estrogen / Q000037:antagonists & inhibitors / Q000378:metabolism; D013237:Stereoisomerism; D013378:Substantia Nigra / Q000166:cytology*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D061945:Caspase Inhibitors; D016895:Culture Media, Serum-Free; D004965:Estrogen Antagonists; D047629:Estrogen Receptor beta; D018696:Neuroprotective Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D016755:Proto-Oncogene Proteins c-jun; D011960:Receptors, Estrogen; D018808:Transcription Factor AP-1; D001761:Bleomycin; D004958:Estradiol; D019328:Buthionine Sulfoximine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D004298:Dopamine