Ethanol triggers neural crest apoptosis through the selective activation of a pertussis toxin-sensitive G protein and a phospholipase Cbeta-dependent Ca2+ transient

Alcohol is a potent neurotoxin that triggers the selective apoptosis of neuronal populations in the developing fetus. For neural crest cells, clinically relevant ethanol levels (0.3%) rapidly elicit a phospholipase C (PLC)-dependent intracellular Ca2+ transient that is sufficient to activate apoptos...

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Bibliographic Details
Published in:Alcoholism, clinical and experimental research clinical and experimental research, 2005-07, Vol.29 (7), p.1237
Main Authors: Garic-Stankovic, Ana, Hernandez, Marcos R, Chiang, Po Jen, Debelak-Kragtorp, Katherine A, Flentke, George R, Armant, D Randall, Smith, Susan M
Format: Article
Language:English
Subjects:
Animals
Apoptosis - drug effects
Calcium - metabolism
Chick Embryo
Disease Models, Animal
Enzyme Activation - drug effects
Estrenes - pharmacology
Ethanol - toxicity
Female
Fetal Alcohol Spectrum Disorders - physiopathology
GTP-Binding Proteins - metabolism
Humans
Isoenzymes - physiology
Neural Crest - drug effects
Neural Crest - pathology
Pertussis Toxin - pharmacology
Phospholipase C beta
Phospholipid Ethers - pharmacology
Pregnancy
Pyrrolidinones - pharmacology
Type C Phospholipases - physiology
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Summary:Alcohol is a potent neurotoxin that triggers the selective apoptosis of neuronal populations in the developing fetus. For neural crest cells, clinically relevant ethanol levels (0.3%) rapidly elicit a phospholipase C (PLC)-dependent intracellular Ca2+ transient that is sufficient to activate apoptosis. We investigated the biochemical origins of this Ca2+ transient. Three somite chick embryos (stage 8-) were pretreated with agonists and antagonists of PLC signaling pathways before ethanol challenge. The resulting intracellular Ca2+ release was quantified using Fluo-3; apoptosis was assessed using vital dyes. Pretreatment of embryos with PLC antagonists U73122 or ET-18-OCH3 confirmed that a phosphoinositide-specific PLC was required for both the ethanol-dependent Ca2+ transient and subsequent cell death. Ethanol rapidly elevated intracellular inositol-1,4,5-trisphosphate [Ins(1,4,5)P3] levels in the rostral portion of the embryo that contains neural crest progenitors. The Ins(1,4,5)P3 receptor antagonist xestospongin C blocked the appearance of the ethanol-dependent Ca2+ transient. Pretreatment with the pan-Galpha protein antagonist GDPbetaS, but not with the tyrosine kinase antagonist genistein, suppressed ethanol's ability to elicit the Ca2+ transient, suggesting that a rise in PLC activity and Ins(1,4,5)P3 concentration originates from stimulation of heterotrimeric G proteins. To probe the identity of this G protein, embryos were treated with G protein antagonists. Pertussis toxin and NF023 suppressed the ethanol-induced Ca2+ transient and subsequent neural crest apoptosis, whereas suramin was weakly inhibitory. C3 exoenzyme was embryolethal over a wide concentration range, consistent with suggestions that Rho family GTPases participate in neural crest development. Galphai2 was identified by immunostaining in the neural crest cells. We propose a role for Galphai/o protein activation and subsequent interaction of Gbetagamma with PLCbeta in mediating the proapoptotic effects of ethanol upon the developing neural crest.
ISSN:0145-6008
1530-0277