007 - Regulation of Anxiety by Membrane Estrogen Receptor Alpha and TrkB Pathways Following Neonatal Hypoxia Ischemia

Publication Number: 7.6527

Nur Sena Cagatay, Children’s Hospital of Michigan, Detroit, MI, United States; Onur Taparli, State University of New York Downstate Medical Center College of Medicine, BROOKLYN, NY, United States; Ela Bicki, State University of New York Downstate Medical Center College of Medicine, Brooklyn, NY, United States; Temour Sheikh, University of Wisconsin Madison, Tulsa, OK, United States; Furkan Camci, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States; Feyza Cetin, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States; Sefer Yapici, University of Wisconsin-Madison, Madison, WI, United States; Peter Ferrazzano, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States; Pelin Cengiz, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States

Background: Neonatal hypoxia ischemia (HI)-related brain injury leads to learning and memory deficits in children. We previously demonstrated that tyrosine kinase B (TrkB)-mediated neuroprotection is sex specific and dependent on estrogen receptor alpha (ERa) in the hippocampus after neonatal HI.

Objective: In this study, we hypothesized that sex-specific ERa-dependent and TrkB-mediated long-term neuroprotection is regulated by membrane ERa.To test this hypothesis, we used ERa wild type (WT), ERa complete knockout (ERKO), and nuclear-only ERa (NOER) mice that expresses ERa only in the nucleus to investigate downstream signaling pathways of TrkB and long-term anxiety-like behavior.

Design/Methods: Postnatal day (P) 9 male and female WT, ERKO, and NOER mice underwent either sham or HI surgery (n=6-10). Mice were given either a vehicle control or a TrkB agonist, 7,8-dihydroxyflavone (7,8-DHF), daily for three or seven days after 10 minutes of HI or sham surgery for subsequent behavioral assessment and imaging. Hippocampal AKT1/3, ERK1/2, truncated TrkB (T1.TrkB) and full-length TrkB (FL.TrkB) mRNA, and total TrkB (FL.TrkB, T.TrkB), and actin protein expressions were measured at P12. Elevated Plus Maze Testing was performed at P90+, followed by T2 weighted brain MRI. ITK-SNAP was used to calculate hippocampal and hemispheric volume reductions as a percentage. For multi-group comparisons, ANOVA was used.

Results: Our results show that; 1) HI increases hippocampal AKT1 mRNA but decreases AKT3 mRNA in both WT male and females compared to sham 3 days after HI. 7,8-DHF further increases AKT1 mRNA and reduces AKT3 mRNA expression in female hippocampi after HI (p < 0.001). This change of hippocampal AKT1 mRNA and AKT3 mRNA in females is abolished in ERKO and NOER mice. HI increases the T1.TrkB mRNA expression and decreases the FL.TrkB expression in WT male and female mice. 2) HI increases hippocampal T.TrkB protein in both WT male and female mice. 7,8-DHF decreases T.TrkB/actin protein expression only in the female hippocampus post-HI (p=0.01). 3) WT female mice spent more time in the open arm post-HI (p=0.0009) that is recovered by the 7,8-DHF therapy in a membrane ERa dependent manner (p=0.05). 4) The % time spent in the open arm positively correlates with the hemispheric and hippocampal injury (R2: 0.42 p< 0.001, R2: 0.32 P< 0.001).

Conclusion(s): Our findings demonstrate that membrane ERa maybe mediating the female-biased TrkB-mediated hippocampal neuroprotection through T.TrkB.