Abstract
Male neonate brains are more susceptible to the effects of perinatal asphyxia resulting in hypoxia and ischemia (HI)-related brain injury. The relative resistance of female neonatal brains to adverse consequences of HI suggests that there are sex-specific mechanisms that afford females greater neuroprotection and/or facilitates recovery post-HI. We hypothesized that HI preferentially induces estrogen receptor α (ERα) expression in female neonatal hippocampi and that ERα is coupled to Src family kinase (SFK) activation that in turn augments phosphorylation of the TrkB and thereby results in decreased apoptosis. After inducing the Vannucci’s HI model on P9 (C57BL/6J) mice, female and male ERα wild-type (ERα+/+) or ERα null mutant (ERα−/−) mice received vehicle control or the selective TrkB agonist 7,8-dihydroxyflavone (7,8-DHF). Hippocampi were collected for analysis of mRNA of ERα and BDNF, protein levels of ERα, p-TrkB, p-src, and cleaved caspase 3 (c-caspase-3) post-HI. Our results demonstrate that: (1) HI differentially induces ERα expression in the hippocampus of the female versus male neonate, (2) src and TrkB phosphorylation post-HI is greater in females than in males after 7,8-DHF therapy, (3) src and TrkB phosphorylation post-HI depend on the presence of ERα, and (4) TrkB agonist therapy decreases the c-caspase-3 only in ERα+/+ female mice hippocampus. Together, these observations provide evidence that female-specific induction of ERα expression confers neuroprotection with TrkB agonist therapy via SFK activation and account for improved functional outcomes in female neonates post-HI.
Footnotes
↵1 The authors report no conflict of interest.
↵3 This work was supported by a University of Wisconsin Department of Pediatrics Research & Development Grant (P.C.), Clinical and Translational Science Award program of NCATS UL1 TR0000427 and KL2 TR000428 (P.C.), UL1TR000427 to the UW ICTR from NIH/NCATS and funds from Waisman Center (P.C.), NIH/NINDS K08NS088563-01A1 (P.C.) and NIH P30 HD03352 (Waisman Center), NIH/NINDS 1K08NS078113 (P.F.). We thank Drs John Svaren and Matthew Flowers for invaluable technical support that they provided for the qPCR experiments and chemiluminescence imaging, respectively.
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