PT  - JOURNAL ARTICLE
AU  - Teresa Jover
AU  - Hidenobu Tanaka
AU  - Agata Calderone
AU  - Keiji Oguro
AU  - Michael V. L. Bennett
AU  - Anne M. Etgen
AU  - R. Suzanne Zukin
TI  - Estrogen Protects against Global Ischemia-Induced Neuronal Death and Prevents Activation of Apoptotic Signaling Cascades in the Hippocampal CA1
AID  - 10.1523/JNEUROSCI.22-06-02115.2002
DP  - 2002 Mar 15
TA  - The Journal of Neuroscience
PG  - 2115--2124
VI  - 22
IP  - 6
4099  - http://www.jneurosci.org/content/22/6/2115.short
4100  - http://www.jneurosci.org/content/22/6/2115.full
SO  - J. Neurosci.2002 Mar 15; 22
AB  - The importance of postmenopausal estrogen replacement therapy in affording protection against the selective and delayed neuronal death associated with cardiac arrest or cardiac surgery in women remains controversial. Here we report that exogenous estrogen at levels that are physiological for hormone replacement in postmenopausal women affords protection against global ischemia-induced neuronal death and prevents activation of apoptotic signaling cascades in the hippocampal CA1 of male gerbils. Global ischemia induced a marked increase in activated caspase-3 in CA1, evident at 6 hr after ischemia. Global ischemia induced a marked upregulation of the proapoptotic neurotrophin receptor p75NTR in CA1, evident at 48 hr. p75NTR expression was induced primarily in terminal deoxynucleotidyl transferase-mediated UTP nick-end labeling-positive cells, indicating expression in neurons undergoing apoptosis. Global ischemia also induced a marked downregulation of mRNA encoding the AMPA receptor GluR2 subunit in CA1. Caspase-3, p75NTR, and GluR2 were not significantly changed in CA3 and dentate gyrus, indicating that the ischemia-induced changes in gene expression were cell specific. Exogenous estrogen attenuated the ischemia-induced increases in activated caspase-3 and blocked the increase in p75NTR in post-ischemic CA1 neurons but did not prevent ischemia-induced downregulation of GluR2. These findings demonstrate that long-term estrogen at physiological levels ameliorates ischemia-induced hippocampal injury and indicate that estrogen intervenes at the level of apoptotic signaling cascades to prevent onset of death in neurons otherwise “destined to die.”