title: Estrogen protects against dopamine neuron toxicity in primary mesencephalic cultures through an indirect P13K/Akt mediated astrocyte pathway.
abstract: Astrocytes regulate neuronal homeostasis and have been implicated in affecting the viability and functioning of surrounding neurons under stressed and injured conditions. Previous data from our lab suggests indirect actions of estrogen through ERα in neighboring astroglia to protect dopamine neurons against 1-methyl-4-phenylpyridinium (MPP(+)) toxicity in mouse mesencephalic cultures. We further evaluate estrogen signaling in astrocytes and the mechanism of estrogen's indirect neuroprotective effects on dopamine neurons. Primary mesencephalic cultures pre-treated with 17β-estradiol and the membrane impermeable estrogen, E2-BSA, were both neuroprotective against MPP(+) -induced dopamine neuron toxicity, suggesting membrane-initiated neuroprotection. ERα was found in the plasma membrane of astrocyte cultures and colocalized with the lipid raft marker, flotillin-1. A 17β-estradiol time course revealed a significant increase in Akt, which was inhibited by the PI3 kinase inhibitor, LY294004. Estrogen conditioned media collected from pure astrocyte cultures rescued glial deficient mesencephalic cultures from MPP(+). This indirect estrogen-mediated neuroprotective effect in mesencephalic cultures was significantly reduced when PI3 kinase signaling in astrocytes was blocked prior to collecting estrogen-conditioned media using the irreversible PI3 kinase inhibitor, Wortmannin. Estrogen signaling via astrocytes is rapidly initiated at the membrane level and requires PI3 kinase signaling in order to protect primary mesencephalic dopamine neurons from MPP(+) neurotoxicity.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, United states. Electronic address: bbains@uiwtx.edu.
authors.forename: Mona
authors.initials: M
authors.lastname: Bains
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, United states.
authors.forename: James L
authors.initials: JL
authors.lastname: Roberts
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D017077:Culture Media, Conditioned; D059290:Dopaminergic Neurons / Q000166:cytology / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology*; D008636:Mesencephalon / Q000166:cytology; D008810:Mice, Inbred C57BL; D018696:Neuroprotective Agents / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D061251:Primary Cell Culture; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D015398:Signal Transduction; D000077191:Wortmannin
chemical_list: D015655:1-Methyl-4-phenylpyridinium; D000730:Androstadienes; D017077:Culture Media, Conditioned; D004958:Estradiol; D047628:Estrogen Receptor alpha; D004967:Estrogens; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D012710:Serum Albumin, Bovine; D000077191:Wortmannin; C043090:estradiol-bovine serum albumin
keywords: Astrocytes; Dopamine neurons; Estrogen; Neuroprotection